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Benefit Plans | 12 Months Ended
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Dec. 31, 2015
Benefit Plans | BENEFIT PLANS (a) Pension and Other Postretirement Benefits Plans - Retirement benefits are provided to substantially all employees through various qualified and non-qualified non-contributory defined benefit pension plans, and/or through defined contribution plans (including 401(k) savings plans). Qualified and non-qualified non-contributory defined benefit pension plans are currently closed to new hires. Benefits of the non-contributory defined benefit pension plans are based on the plan participant’s years of service, age and compensation. Benefits of the defined contribution plans are based on the plan participant’s years of service, age, compensation and contributions. Certain defined benefit postretirement health care and life benefits are provided to eligible retirees. In general, the retiree health care plans consist of fixed benefit subsidy structures and the retiree life insurance plans are non-contributory. IPL and WPL account for their participation in Alliant Energy and Corporate Services sponsored plans as multiple-employer plans. Assumptions - The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows:
| Defined Benefit Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.47% |  | 4.18% |  | 4.97% |  | 4.30% |  | 3.97% |  | 4.59%
Discount rate for net periodic cost | 4.18% |  | 4.97% |  | 4.11% |  | 3.97% |  | 4.59% |  | 3.82%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 6.20% |  | 7.40% |  | 7.40%
Rate of compensation increase | 3.65 | % | - | 4.50% |  | 3.50 | % | - | 4.50% |  | 3.50 | % | - | 4.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
| Qualified Defined Benefit Pension Plan |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.50% |  | 4.20% |  | 5.05% |  | 4.28% |  | 3.94% |  | 4.55%
Discount rate for net periodic cost | 4.20% |  | 5.05% |  | 4.20% |  | 3.94% |  | 4.55% |  | 3.76%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 6.60% |  | 7.60% |  | 7.50%
Rate of compensation increase | 3.65% |  | 3.50% |  | 3.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
| Qualified Defined Benefit Pension Plan |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.51% |  | 4.20% |  | 5.05% |  | 4.28% |  | 3.96% |  | 4.56%
Discount rate for net periodic cost | 4.20% |  | 5.05% |  | 4.20% |  | 3.96% |  | 4.56% |  | 3.81%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 4.60% |  | 7.30% |  | 7.20%
Rate of compensation increase | 3.65% |  | 3.50% |  | 3.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
Expected rate of return on plan assets - The expected rate of return on plan assets is determined by analysis of projected asset class returns based on the target asset class allocations. A forward-looking building blocks approach is used, and historical returns, survey information and capital market information are reviewed to support the expected rate of return on plan assets assumption. Refer to “Investment Policy and Strategy for Plan Assets” below for additional information related to investment policy, and strategy and mix of assets for the pension and OPEB plans. Life Expectancy - The life expectancy assumption is used in determining the benefit obligation and net periodic benefit cost for defined benefit pension and OPEB plans. This assumption was updated as of December 31, 2014 and 2015 to utilize new mortality tables that were released in 2014 by the Society of Actuaries and updated in 2015, respectively. Net Periodic Benefit Costs (Credits) - The components of net periodic benefit costs (credits) for sponsored defined benefit pension and OPEB plans are included in the tables below (in millions). In IPL’s and WPL’s tables below, the defined benefit pension plans costs represent those respective costs for their bargaining unit employees covered under the qualified plans that they sponsor, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In IPL’s and WPL’s tables below, the OPEB plans costs (credits) represent respective costs (credits) for their employees, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Corporate Services sponsored OPEB plan.
Alliant Energy | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $15.9 |  |  |  | $13.1 |  |  |  | $15.7 |  |  |  | $5.5 |  |  |  | $5.2 |  |  |  | $6.3 |
Interest cost | 53.6 |  |  | 54.1 |  |  | 49.0 |  |  | 9.1 |  |  | 9.5 |  |  | 8.5 |
Expected return on plan assets (a) | (75.0 | ) |  | (74.9 | ) |  | (74.0 | ) |  | (8.4 | ) |  | (8.3 | ) |  | (8.1 | )
Amortization of prior service cost (credit) (b) | (0.2 | ) |  | — |  |  | 0.2 |  |  | (11.3 | ) |  | (11.9 | ) |  | (11.9 | )
Amortization of actuarial loss (c) | 35.4 |  |  | 19.5 |  |  | 36.2 |  |  | 4.8 |  |  | 2.4 |  |  | 4.9 |
Additional benefit costs (d) | 0.5 |  |  | — |  |  | 9.0 |  |  | — |  |  | — |  |  | — |
|  | $30.2 |  |  |  | $11.8 |  |  |  | $36.1 |  |  |  | ($0.3 | ) |  |  | ($3.1 | ) |  |  | ($0.3 | )
IPL | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $8.8 |  |  |  | $7.2 |  |  |  | $8.6 |  |  |  | $2.4 |  |  |  | $2.4 |  |  |  | $2.9 |
Interest cost | 25.0 |  |  | 25.1 |  |  | 22.9 |  |  | 3.8 |  |  | 3.9 |  |  | 3.6 |
Expected return on plan assets (a) | (35.8 | ) |  | (35.7 | ) |  | (35.2 | ) |  | (5.7 | ) |  | (5.8 | ) |  | (5.6 | )
Amortization of prior service cost (credit) (b) | (0.1 | ) |  | — |  |  | 0.1 |  |  | (6.1 | ) |  | (6.3 | ) |  | (6.3 | )
Amortization of actuarial loss (c) | 15.3 |  |  | 8.0 |  |  | 15.2 |  |  | 2.3 |  |  | 1.1 |  |  | 2.7 |
Additional benefit costs (d) | — |  |  | — |  |  | 2.6 |  |  | — |  |  | — |  |  | — |
|  | $13.2 |  |  |  | $4.6 |  |  |  | $14.2 |  |  |  | ($3.3 | ) |  |  | ($4.7 | ) |  |  | ($2.7 | )
WPL | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $5.8 |  |  |  | $4.9 |  |  |  | $5.9 |  |  |  | $2.1 |  |  |  | $2.0 |  |  |  | $2.5 |
Interest cost | 22.6 |  |  | 22.6 |  |  | 20.7 |  |  | 3.7 |  |  | 3.8 |  |  | 3.4 |
Expected return on plan assets (a) | (32.4 | ) |  | (32.4 | ) |  | (31.9 | ) |  | (1.5 | ) |  | (1.3 | ) |  | (1.3 | )
Amortization of prior service cost (credit) (b) | 0.2 |  |  | 0.3 |  |  | 0.3 |  |  | (3.5 | ) |  | (3.9 | ) |  | (3.9 | )
Amortization of actuarial loss (c) | 16.8 |  |  | 9.2 |  |  | 17.1 |  |  | 2.2 |  |  | 1.3 |  |  | 1.9 |
Additional benefit costs (d) | 0.5 |  |  | — |  |  | 0.6 |  |  | — |  |  | — |  |  | — |
|  | $13.5 |  |  |  | $4.6 |  |  |  | $12.7 |  |  |  | $3.0 |  |  |  | $1.9 |  |  |  | $2.6 |
(a) | The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets.
(b) | Unrecognized prior service costs (credits) for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan.
(c) | Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Cash Balance Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits.
(d) | In 2013, Alliant Energy filed a stipulation agreement with the Western Wisconsin Court related to a class-action lawsuit against the Cash Balance Plan. As a result, Alliant Energy recognized $9.0 million of additional benefits costs in 2013 related to the agreement. IPL recognized $5.5 million ($2.6 million directly assigned and $2.9 million allocated by Corporate Services) and WPL recognized $2.8 million ($0.6 million directly assigned and $2.2 million allocated by Corporate Services) of additional benefits costs in 2013 related to the agreement.
The estimated amortization from “Regulatory assets” and “Regulatory liabilities” on the balance sheets and AOCL on Alliant Energy’s balance sheet into net periodic benefit cost in 2016 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Defined Benefit |  |  |  | Defined Benefit |  |  |  | Defined Benefit |  |
| Pension Plans |  | OPEB Plans |  | Pension Plans |  | OPEB Plans |  | Pension Plans |  | OPEB Plans
Actuarial loss |  | $37.4 |  |  |  | $4.8 |  |  |  | $16.5 |  |  |  | $2.6 |  |  |  | $17.6 |  |  |  | $1.8 |
Prior service cost (credit) | (0.3 | ) |  | (4.1 | ) |  | (0.2 | ) |  | (2.6 | ) |  | 0.2 |  |  | (0.9 | )
|  | $37.1 |  |  |  | $0.7 |  |  |  | $16.3 |  |  |  | $— |  |  |  | $17.8 |  |  |  | $0.9 |
Net periodic benefit costs are primarily included in “Other operation and maintenance” in the income statements. Benefit Plan Assets and Obligations - A reconciliation of the funded status of Alliant Energy’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on Alliant Energy’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $1,301.5 |  |  |  | $1,113.4 |  |  |  | $231.1 |  |  |  | $208.7 |
Service cost | 15.9 |  |  | 13.1 |  |  | 5.5 |  |  | 5.2 |
Interest cost | 53.6 |  |  | 54.1 |  |  | 9.1 |  |  | 9.5 |
Plan participants’ contributions | — |  |  | — |  |  | 3.1 |  |  | 2.8 |
Plan amendments | — |  |  | — |  |  | (0.3 | ) |  | — |
Additional benefit costs | 0.5 |  |  | — |  |  | — |  |  | — |
Actuarial (gain) loss | (70.1 | ) |  | 195.8 |  |  | (9.4 | ) |  | 22.3 |
Gross benefits paid | (95.1 | ) |  | (74.9 | ) |  | (17.7 | ) |  | (17.4 | )
Net benefit obligation at December 31 | 1,206.3 |  |  | 1,301.5 |  |  | 221.4 |  |  | 231.1 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 1,018.1 |  |  | 1,022.9 |  |  | 121.6 |  |  | 124.9 |
Actual return on plan assets | (30.2 | ) |  | 66.4 |  |  | (4.9 | ) |  | 5.6 |
Employer contributions | 2.2 |  |  | 3.7 |  |  | 4.8 |  |  | 5.7 |
Plan participants’ contributions | — |  |  | — |  |  | 3.1 |  |  | 2.8 |
Gross benefits paid | (95.1 | ) |  | (74.9 | ) |  | (17.7 | ) |  | (17.4 | )
Fair value of plan assets at December 31 | 895.0 |  |  | 1,018.1 |  |  | 106.9 |  |  | 121.6 |
Under funded status at December 31 |  | ($311.3 | ) |  |  | ($283.4 | ) |  |  | ($114.5 | ) |  |  | ($109.5 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $3.0 |  |  |  | $6.1 |
Other current liabilities | (2.6 | ) |  | (2.5 | ) |  | (6.2 | ) |  | (5.6 | )
Pension and other benefit obligations | (308.7 | ) |  | (280.9 | ) |  | (111.3 | ) |  | (110.0 | )
Net amounts recognized at December 31 |  | ($311.3 | ) |  |  | ($283.4 | ) |  |  | ($114.5 | ) |  |  | ($109.5 | )
Amounts recognized in Regulatory Assets and AOCL consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $533.1 |  |  |  | $533.4 |  |  |  | $59.8 |  |  |  | $60.7 |
Prior service credit | (7.2 | ) |  | (7.4 | ) |  | (5.6 | ) |  | (16.7 | )
|  | $525.9 |  |  |  | $526.0 |  |  |  | $54.2 |  |  |  | $44.0 |
(a) | Refer to Note 2 and Alliant Energy’s common equity statements for amounts recognized in “Regulatory assets” and “AOCL,” respectively, on Alliant Energy’s balance sheets.
In IPL’s and WPL’s tables below, the defined benefit pension plans amounts represent those respective amounts for their bargaining unit employees covered under the qualified plans that they sponsor, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In IPL’s and WPL’s tables below, the OPEB plans amounts represent respective amounts for their employees, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Corporate Services sponsored OPEB plan. A reconciliation of the funded status of IPL’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on IPL’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $603.1 |  |  |  | $514.0 |  |  |  | $96.4 |  |  |  | $87.8 |
Service cost | 8.8 |  |  | 7.2 |  |  | 2.4 |  |  | 2.4 |
Interest cost | 25.0 |  |  | 25.1 |  |  | 3.8 |  |  | 3.9 |
Plan participants’ contributions | — |  |  | — |  |  | 1.0 |  |  | 0.9 |
Plan amendments | — |  |  | — |  |  | (0.1 | ) |  | — |
Actuarial (gain) loss | (32.3 | ) |  | 91.4 |  |  | (4.6 | ) |  | 8.6 |
Gross benefits paid | (48.5 | ) |  | (34.6 | ) |  | (7.6 | ) |  | (7.2 | )
Net benefit obligation at December 31 | 556.1 |  |  | 603.1 |  |  | 91.3 |  |  | 96.4 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 484.7 |  |  | 485.9 |  |  | 78.7 |  |  | 81.2 |
Actual return on plan assets | (14.3 | ) |  | 32.1 |  |  | (3.1 | ) |  | 3.6 |
Employer contributions | 0.8 |  |  | 1.3 |  |  | 0.2 |  |  | 0.2 |
Plan participants’ contributions | — |  |  | — |  |  | 1.0 |  |  | 0.9 |
Gross benefits paid | (48.5 | ) |  | (34.6 | ) |  | (7.6 | ) |  | (7.2 | )
Fair value of plan assets at December 31 | 422.7 |  |  | 484.7 |  |  | 69.2 |  |  | 78.7 |
Under funded status at December 31 |  | ($133.4 | ) |  |  | ($118.4 | ) |  |  | ($22.1 | ) |  |  | ($17.7 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $— |  |  |  | $1.2 |
Other current liabilities | (0.8 | ) |  | (0.8 | ) |  | — |  |  | — |
Pension and other benefit obligations | (132.6 | ) |  | (117.6 | ) |  | (22.1 | ) |  | (18.9 | )
Net amounts recognized at December 31 |  | ($133.4 | ) |  |  | ($118.4 | ) |  |  | ($22.1 | ) |  |  | ($17.7 | )
Amounts recognized in Regulatory Assets consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $235.5 |  |  |  | $233.1 |  |  |  | $29.8 |  |  |  | $27.9 |
Prior service credit | (2.5 | ) |  | (2.6 | ) |  | (2.7 | ) |  | (8.7 | )
|  | $233.0 |  |  |  | $230.5 |  |  |  | $27.1 |  |  |  | $19.2 |
(a) | Refer to Note 2 for amounts recognized in “Regulatory assets” on IPL’s balance sheets.
A reconciliation of the funded status of WPL’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on WPL’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $547.6 |  |  |  | $460.8 |  |  |  | $94.0 |  |  |  | $85.6 |
Service cost | 5.8 |  |  | 4.9 |  |  | 2.1 |  |  | 2.0 |
Interest cost | 22.6 |  |  | 22.6 |  |  | 3.7 |  |  | 3.8 |
Plan participants’ contributions | — |  |  | — |  |  | 1.6 |  |  | 1.3 |
Plan amendments | — |  |  | — |  |  | (0.2 | ) |  | — |
Additional benefit costs | 0.5 |  |  | — |  |  | — |  |  | — |
Actuarial (gain) loss | (30.0 | ) |  | 86.7 |  |  | (3.5 | ) |  | 9.2 |
Gross benefits paid | (40.6 | ) |  | (27.4 | ) |  | (8.0 | ) |  | (7.9 | )
Net benefit obligation at December 31 | 505.9 |  |  | 547.6 |  |  | 89.7 |  |  | 94.0 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 440.3 |  |  | 438.8 |  |  | 21.8 |  |  | 21.7 |
Actual return on plan assets | (13.0 | ) |  | 28.6 |  |  | (1.1 | ) |  | 1.2 |
Employer contributions | 0.1 |  |  | 0.3 |  |  | 4.4 |  |  | 5.5 |
Plan participants’ contributions | — |  |  | — |  |  | 1.6 |  |  | 1.3 |
Gross benefits paid | (40.6 | ) |  | (27.4 | ) |  | (8.0 | ) |  | (7.9 | )
Fair value of plan assets at December 31 | 386.8 |  |  | 440.3 |  |  | 18.7 |  |  | 21.8 |
Under funded status at December 31 |  | ($119.1 | ) |  |  | ($107.3 | ) |  |  | ($71.0 | ) |  |  | ($72.2 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $3.0 |  |  |  | $4.9 |
Other current liabilities | (0.1 | ) |  | (0.1 | ) |  | (6.0 | ) |  | (5.5 | )
Pension and other benefit obligations | (119.0 | ) |  | (107.2 | ) |  | (68.0 | ) |  | (71.6 | )
Net amounts recognized at December 31 |  | ($119.1 | ) |  |  | ($107.3 | ) |  |  | ($71.0 | ) |  |  | ($72.2 | )
Amounts recognized in Regulatory Assets consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $232.1 |  |  |  | $233.5 |  |  |  | $23.3 |  |  |  | $26.3 |
Prior service credit | (1.2 | ) |  | (1.0 | ) |  | (2.4 | ) |  | (5.6 | )
|  | $230.9 |  |  |  | $232.5 |  |  |  | $20.9 |  |  |  | $20.7 |
(a) | Refer to Note 2 for amounts recognized in “Regulatory assets” on WPL’s balance sheets.
Included in the following tables are accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $1,166.0 |  |  |  | $1,255.0 |  |  |  | $221.4 |  |  |  | $231.1 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 1,166.0 |  |  | 1,255.0 |  |  | 221.4 |  |  | 231.1 |
Fair value of plan assets | 895.0 |  |  | 1,018.1 |  |  | 106.9 |  |  | 121.6 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 1,206.3 |  |  | 1,301.5 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 895.0 |  |  | 1,018.1 |  |  | N/A |  |  | N/A |
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $531.0 |  |  |  | $575.5 |  |  |  | $91.3 |  |  |  | $96.4 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 531.0 |  |  | 575.5 |  |  | 91.3 |  |  | 96.4 |
Fair value of plan assets | 422.7 |  |  | 484.7 |  |  | 69.2 |  |  | 78.7 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 556.1 |  |  | 603.1 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 422.7 |  |  | 484.7 |  |  | N/A |  |  | N/A |
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $493.8 |  |  |  | $532.5 |  |  |  | $89.7 |  |  |  | $94.0 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 493.8 |  |  | 532.5 |  |  | 89.7 |  |  | 94.0 |
Fair value of plan assets | 386.8 |  |  | 440.3 |  |  | 18.7 |  |  | 21.8 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 505.9 |  |  | 547.6 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 386.8 |  |  | 440.3 |  |  | N/A |  |  | N/A |
In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions):
| IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014
Regulatory assets |  | $38.0 |  |  |  | $38.2 |  |  |  | $29.5 |  |  |  | $28.0 |
Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2016 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Defined benefit pension plans (a) |  | $2.6 |  |  |  | $0.8 |  |  |  | $0.1 |
OPEB plans | 5.8 |  |  | — |  |  | 5.5 |
(a) | Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans.
Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions):
Alliant Energy | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $69.5 |  |  |  | $74.3 |  |  |  | $72.8 |  |  |  | $74.3 |  |  |  | $78.7 |  |  |  | $401.4 |
OPEB | 17.8 |  |  | 18.1 |  |  | 18.2 |  |  | 18.3 |  |  | 18.2 |  |  | 86.9 |
|  | $87.3 |  |  |  | $92.4 |  |  |  | $91.0 |  |  |  | $92.6 |  |  |  | $96.9 |  |  |  | $488.3 |
IPL | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $32.8 |  |  |  | $34.1 |  |  |  | $34.8 |  |  |  | $34.6 |  |  |  | $37.8 |  |  |  | $190.8 |
OPEB | 7.6 |  |  | 7.6 |  |  | 7.6 |  |  | 7.5 |  |  | 7.6 |  |  | 36.0 |
|  | $40.4 |  |  |  | $41.7 |  |  |  | $42.4 |  |  |  | $42.1 |  |  |  | $45.4 |  |  |  | $226.8 |
WPL | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $29.1 |  |  |  | $29.8 |  |  |  | $30.7 |  |  |  | $31.1 |  |  |  | $32.2 |  |  |  | $163.7 |
OPEB | 7.5 |  |  | 7.8 |  |  | 7.8 |  |  | 7.8 |  |  | 7.6 |  |  | 34.7 |
|  | $36.6 |  |  |  | $37.6 |  |  |  | $38.5 |  |  |  | $38.9 |  |  |  | $39.8 |  |  |  | $198.4 |
Investment Policy and Strategy for Plan Assets - Investment policies and strategies employed with respect to assets of defined benefit pension and OPEB plans are to combine both preservation of principal and prudent and reasonable risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term. It is recognized that risk and volatility are present with all types of investments. However, risk is mitigated at the total fund level through diversification by asset class including U.S. and international equity and fixed income exposure, global asset and risk parity strategies, the number of individual investments, and sector and industry limits. Global asset and risk parity strategies include investments in global equity, global debt, commodities and currencies. Defined Benefit Pension Plan Assets - For assets of defined benefit pension plans, the mix among asset classes is controlled by asset allocation targets. Historical performance results and future expectations suggest that equity securities will provide higher total investment returns than debt securities over a long-term investment horizon. Consistent with the goals of meeting obligations to plan participants and minimizing benefit costs over the long-term, the defined benefit pension plans have a long-term investment posture more heavily weighted towards equity holdings. The asset allocation is monitored regularly and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. An overlay management service is also used to help maintain target allocations and meet liquidity needs. The overlay manager is authorized to use derivative financial instruments to facilitate this service. For separately managed accounts, prohibited investment vehicles include, but may not be limited to, direct ownership of real estate, margin trading, oil and gas limited partnerships and securities of the managers’ firms or affiliate firms. At December 31, 2015, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows:
| Target Range |  | Actual
| Allocation |  | Allocation
Cash and equivalents | 0 | % | - | 5% |  | 2%
Equity securities: |  |  |  |  |
U.S. large cap core | 8 | % | - | 18% |  | 11%
U.S. large cap value | 2.5 | % | - | 12.5% |  | 7%
U.S. large cap growth | 2.5 | % | - | 12.5% |  | 7%
U.S. small cap value | 0 | % | - | 4% |  | 1%
U.S. small cap growth | 0 | % | - | 4% |  | 2%
International - developed markets | 7 | % | - | 19% |  | 12%
International - emerging markets | 0 | % | - | 10% |  | 5%
Global asset allocation securities | 5 | % | - | 15% |  | 11%
Risk parity allocation securities | 5 | % | - | 15% |  | 10%
Fixed income securities | 20 | % | - | 40% |  | 32%
Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts. The investment policy and strategy of the 401(h) assets, except for the WPL 401(h) assets, mirrors those of the defined benefit pension plans, which are discussed above. For VEBA trusts with assets greater than $5 million and the WPL 401(h) assets, the mix among asset classes is controlled by allocation targets. The asset allocation is monitored regularly and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. Mutual funds are used to achieve the desired diversification. At December 31, 2015, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows:
| Target Range |  | Actual
| Allocation |  | Allocation
Cash and equivalents | 0 | % | - | 15% |  | 3%
Equity securities: |  |  |  |  |
Domestic | 0 | % | - | 45% |  | 21%
International | 0 | % | - | 21% |  | 13%
Global asset allocation securities | 5 | % | - | 40% |  | 16%
Fixed income securities | 10 | % | - | 70% |  | 47%
Fair Value Measurements - The following tables report a framework for measuring fair value. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy and examples of each are as follows: Level 1 - Pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. Investments in securities held in registered investment companies and directly held equity securities are valued at the closing price reported in the active market in which the securities are traded. Level 2 - Pricing inputs are quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability and inputs that are derived principally from or corroborated by observable market data by correlation or other means. Investments in common/collective trusts are valued at the net asset value of shares held by the plans, which is based on the fair market value of the underlying investments in the common/collective trusts. Investments in corporate bonds are valued at the closing price reported in the active market for similar assets in which the individual securities are traded or based on yields currently available on comparable securities of issuers with similar credit ratings. Level 3 - Pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while Alliant Energy, IPL and WPL believe their valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date. At December 31, the fair values of Alliant Energy’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $23.1 |  |  |  | $— |  |  |  | $23.1 |  |  |  | $— |  |  |  | $49.3 |  |  |  | $— |  |  |  | $49.3 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 100.4 |  |  | 100.4 |  |  | — |  |  | — |  |  | 137.2 |  |  | 137.2 |  |  | — |  |  | — |
U.S. large cap value | 59.9 |  |  | — |  |  | 59.9 |  |  | — |  |  | 72.2 |  |  | — |  |  | 72.2 |  |  | — |
U.S. large cap growth | 60.5 |  |  | — |  |  | 60.5 |  |  | — |  |  | 73.2 |  |  | — |  |  | 73.2 |  |  | — |
U.S. small cap value | 14.2 |  |  | — |  |  | 14.2 |  |  | — |  |  | 15.2 |  |  | — |  |  | 15.2 |  |  | — |
U.S. small cap growth | 16.0 |  |  | 16.0 |  |  | — |  |  | — |  |  | 15.9 |  |  | 15.9 |  |  | — |  |  | — |
International - developed markets | 104.4 |  |  | 52.7 |  |  | 51.7 |  |  | — |  |  | 102.9 |  |  | 52.1 |  |  | 50.8 |  |  | — |
International - emerging markets | 41.2 |  |  | 41.2 |  |  | — |  |  | — |  |  | 47.2 |  |  | 47.2 |  |  | — |  |  | — |
Global asset allocation securities | 96.3 |  |  | 52.9 |  |  | 43.4 |  |  | — |  |  | 99.9 |  |  | 57.2 |  |  | 42.7 |  |  | — |
Risk parity allocation securities | 94.0 |  |  | — |  |  | 94.0 |  |  | — |  |  | 102.5 |  |  | — |  |  | 102.5 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.1 |  |  | — |
Fixed income funds | 284.8 |  |  | — |  |  | 284.8 |  |  | — |  |  | 302.7 |  |  | 0.2 |  |  | 302.5 |  |  | — |
| 894.8 |  |  |  | $263.2 |  |  |  | $631.6 |  |  |  | $— |  |  | 1,018.3 |  |  |  | $309.8 |  |  |  | $708.5 |  |  |  | $— |
Accrued investment income | 0.2 |  |  |  |  |  |  |  |  | 0.1 |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.3 | ) |  |  |  |  |  |
Total pension plan assets |  | $895.0 |  |  |  |  |  |  |  |  |  | $1,018.1 |  |  |  |  |  |  |
At December 31, the fair values of IPL’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $10.9 |  |  |  | $— |  |  |  | $10.9 |  |  |  | $— |  |  |  | $23.5 |  |  |  | $— |  |  |  | $23.5 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 47.4 |  |  | 47.4 |  |  | — |  |  | — |  |  | 65.3 |  |  | 65.3 |  |  | — |  |  | — |
U.S. large cap value | 28.3 |  |  | — |  |  | 28.3 |  |  | — |  |  | 34.4 |  |  | — |  |  | 34.4 |  |  | — |
U.S. large cap growth | 28.6 |  |  | — |  |  | 28.6 |  |  | — |  |  | 34.9 |  |  | — |  |  | 34.9 |  |  | — |
U.S. small cap value | 6.7 |  |  | — |  |  | 6.7 |  |  | — |  |  | 7.2 |  |  | — |  |  | 7.2 |  |  | — |
U.S. small cap growth | 7.5 |  |  | 7.5 |  |  | — |  |  | — |  |  | 7.6 |  |  | 7.6 |  |  | — |  |  | — |
International - developed markets | 49.3 |  |  | 24.9 |  |  | 24.4 |  |  | — |  |  | 49.0 |  |  | 24.8 |  |  | 24.2 |  |  | — |
International - emerging markets | 19.5 |  |  | 19.5 |  |  | — |  |  | — |  |  | 22.5 |  |  | 22.5 |  |  | — |  |  | — |
Global asset allocation securities | 45.5 |  |  | 25.0 |  |  | 20.5 |  |  | — |  |  | 47.5 |  |  | 27.2 |  |  | 20.3 |  |  | — |
Risk parity allocation securities | 44.4 |  |  | — |  |  | 44.4 |  |  | — |  |  | 48.8 |  |  | — |  |  | 48.8 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 134.5 |  |  | — |  |  | 134.5 |  |  | — |  |  | 144.1 |  |  | 0.1 |  |  | 144.0 |  |  | — |
| 422.6 |  |  |  | $124.3 |  |  |  | $298.3 |  |  |  | $— |  |  | 484.8 |  |  |  | $147.5 |  |  |  | $337.3 |  |  |  | $— |
Accrued investment income | 0.1 |  |  |  |  |  |  |  |  | 0.1 |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.2 | ) |  |  |  |  |  |
Total pension plan assets |  | $422.7 |  |  |  |  |  |  |  |  |  | $484.7 |  |  |  |  |  |  |
At December 31, the fair values of WPL’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $10.0 |  |  |  | $— |  |  |  | $10.0 |  |  |  | $— |  |  |  | $21.3 |  |  |  | $— |  |  |  | $21.3 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 43.4 |  |  | 43.4 |  |  | — |  |  | — |  |  | 59.3 |  |  | 59.3 |  |  | — |  |  | — |
U.S. large cap value | 25.9 |  |  | — |  |  | 25.9 |  |  | — |  |  | 31.3 |  |  | — |  |  | 31.3 |  |  | — |
U.S. large cap growth | 26.2 |  |  | — |  |  | 26.2 |  |  | — |  |  | 31.7 |  |  | — |  |  | 31.7 |  |  | — |
U.S. small cap value | 6.1 |  |  | — |  |  | 6.1 |  |  | — |  |  | 6.6 |  |  | — |  |  | 6.6 |  |  | — |
U.S. small cap growth | 6.9 |  |  | 6.9 |  |  | — |  |  | — |  |  | 6.9 |  |  | 6.9 |  |  | — |  |  | — |
International - developed markets | 45.1 |  |  | 22.8 |  |  | 22.3 |  |  | — |  |  | 44.5 |  |  | 22.5 |  |  | 22.0 |  |  | — |
International - emerging markets | 17.8 |  |  | 17.8 |  |  | — |  |  | — |  |  | 20.4 |  |  | 20.4 |  |  | — |  |  | — |
Global asset allocation securities | 41.6 |  |  | 22.8 |  |  | 18.8 |  |  | — |  |  | 43.2 |  |  | 24.8 |  |  | 18.4 |  |  | — |
Risk parity allocation securities | 40.6 |  |  | — |  |  | 40.6 |  |  | — |  |  | 44.3 |  |  | — |  |  | 44.3 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 123.1 |  |  | — |  |  | 123.1 |  |  | — |  |  | 130.9 |  |  | 0.1 |  |  | 130.8 |  |  | — |
| 386.7 |  |  |  | $113.7 |  |  |  | $273.0 |  |  |  | $— |  |  | 440.4 |  |  |  | $134.0 |  |  |  | $306.4 |  |  |  | $— |
Accrued investment income | 0.1 |  |  |  |  |  |  |  |  | — |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.1 | ) |  |  |  |  |  |
Total pension plan assets |  | $386.8 |  |  |  |  |  |  |  |  |  | $440.3 |  |  |  |  |  |  |
At December 31, the fair values of Alliant Energy’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $3.6 |  |  |  | $— |  |  |  | $3.6 |  |  |  | $— |  |  |  | $3.7 |  |  |  | $— |  |  |  | $3.7 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | 21.1 |  |  | 21.1 |  |  | — |  |  | — |  |  | 35.8 |  |  | 35.8 |  |  | — |  |  | — |
U.S. large cap core | 0.9 |  |  | 0.9 |  |  | — |  |  | — |  |  | 2.9 |  |  | 2.9 |  |  | — |  |  | — |
U.S. large cap value | 0.5 |  |  | — |  |  | 0.5 |  |  | — |  |  | 1.5 |  |  | — |  |  | 1.5 |  |  | — |
U.S. large cap growth | 0.5 |  |  | — |  |  | 0.5 |  |  | — |  |  | 1.6 |  |  | — |  |  | 1.6 |  |  | — |
U.S. small cap value | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. small cap growth | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.4 |  |  | 0.4 |  |  | — |  |  | — |
International - blend | 12.5 |  |  | 12.5 |  |  | — |  |  | — |  |  | 14.2 |  |  | 14.2 |  |  | — |  |  | — |
International - developed markets | 1.0 |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | 2.2 |  |  | 1.1 |  |  | 1.1 |  |  | — |
International - emerging markets | 0.4 |  |  | 0.4 |  |  | — |  |  | — |  |  | 1.0 |  |  | 1.0 |  |  | — |  |  | — |
Global asset allocation securities | 16.4 |  |  | 16.0 |  |  | 0.4 |  |  | — |  |  | 30.3 |  |  | 29.4 |  |  | 0.9 |  |  | — |
Risk parity allocation securities | 0.9 |  |  | — |  |  | 0.9 |  |  | — |  |  | 2.2 |  |  | — |  |  | 2.2 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 48.9 |  |  | 46.3 |  |  | 2.6 |  |  | — |  |  | 25.5 |  |  | 19.0 |  |  | 6.5 |  |  | — |
Total OPEB plan assets |  | $106.9 |  |  |  | $97.8 |  |  |  | $9.1 |  |  |  | $— |  |  |  | $121.6 |  |  |  | $103.8 |  |  |  | $17.8 |  |  |  | $— |
At December 31, the fair values of IPL’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $0.9 |  |  |  | $— |  |  |  | $0.9 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | 16.6 |  |  | 16.6 |  |  | — |  |  | — |  |  | 27.2 |  |  | 27.2 |  |  | — |  |  | — |
U.S. large cap core | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | — |
U.S. large cap value | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. large cap growth | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. small cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.1 |  |  | — |
U.S. small cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | 0.1 |  |  | — |  |  | — |
International - blend | 10.7 |  |  | 10.7 |  |  | — |  |  | — |  |  | 10.7 |  |  | 10.7 |  |  | — |  |  | — |
International - developed markets | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.4 |  |  | 0.2 |  |  | 0.2 |  |  | — |
International - emerging markets | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | 0.2 |  |  | — |  |  | — |
Global asset allocation securities | 6.9 |  |  | 6.9 |  |  | — |  |  | — |  |  | 21.6 |  |  | 21.5 |  |  | 0.1 |  |  | — |
Risk parity allocation securities | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.4 |  |  | — |  |  | 0.4 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 33.6 |  |  | 33.3 |  |  | 0.3 |  |  | — |  |  | 15.5 |  |  | 14.3 |  |  | 1.2 |  |  | — |
Total OPEB plan assets |  | $69.2 |  |  |  | $67.7 |  |  |  | $1.5 |  |  |  | $— |  |  |  | $78.7 |  |  |  | $74.7 |  |  |  | $4.0 |  |  |  | $— |
At December 31, the fair values of WPL’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $2.3 |  |  |  | $— |  |  |  | $2.3 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | — |  |  | — |  |  | — |  |  | — |  |  | 3.6 |  |  | 3.6 |  |  | — |  |  | — |
U.S. large cap core | — |  |  | — |  |  | — |  |  | — |  |  | 1.6 |  |  | 1.6 |  |  | — |  |  | — |
U.S. large cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.8 |  |  | — |  |  | 0.8 |  |  | — |
U.S. large cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.8 |  |  | — |  |  | 0.8 |  |  | — |
U.S. small cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | — |  |  | 0.2 |  |  | — |
U.S. small cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | 0.2 |  |  | — |  |  | — |
International - blend | — |  |  | — |  |  | — |  |  | — |  |  | 1.4 |  |  | 1.4 |  |  | — |  |  | — |
International - developed markets | — |  |  | — |  |  | — |  |  | — |  |  | 1.2 |  |  | 0.6 |  |  | 0.6 |  |  | — |
International - emerging markets | — |  |  | — |  |  | — |  |  | — |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | — |
Global asset allocation securities | 5.4 |  |  | 5.4 |  |  | — |  |  | — |  |  | 3.8 |  |  | 3.3 |  |  | 0.5 |  |  | — |
Risk parity allocation securities | — |  |  | — |  |  | — |  |  | — |  |  | 1.1 |  |  | — |  |  | 1.1 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 11.0 |  |  | 11.0 |  |  | — |  |  | — |  |  | 5.2 |  |  | 1.8 |  |  | 3.4 |  |  | — |
Total OPEB plan assets |  | $18.7 |  |  |  | $16.4 |  |  |  | $2.3 |  |  |  | $— |  |  |  | $21.8 |  |  |  | $13.0 |  |  |  | $8.8 |  |  |  | $— |
For the various defined benefit pension and OPEB plans, Alliant Energy common stock represented less than 1% of assets directly held in the plans at December 31, 2015 and 2014. 401(k) Savings Plans - A significant number of employees participate in defined contribution retirement plans (401(k) savings plans). Alliant Energy common stock represented 11.6% and 12.6% of total assets held in 401(k) savings plans at December 31, 2015 and 2014, respectively. Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  |  | 2014 |  |  | 2013 |  |  | 2015 |  | 2014 |  | 2013
401(k) costs |  | $24.9 |  |  |  | $22.5 |  |  |  | $19.2 |  |  |  | $12.7 |  |  |  | $11.1 |  |  |  | $9.9 |  |  |  | $11.2 |  |  |  | $10.5 |  |  |  | $8.5 |
Voluntary Employee Separation Charges - In 2015, Alliant Energy offered certain employees a voluntary separation package. Approximately 2% of total Alliant Energy employees accepted this package, which resulted in Alliant Energy, IPL and WPL recording charges of $8 million, $5 million and $3 million, respectively, in 2015. (b) Equity-based Compensation Plans - In 2015, Alliant Energy’s shareowners approved the Amended and Restated OIP, which permits the grant of shares of Alliant Energy common stock, restricted stock, restricted stock units, performance shares, performance units, and other stock-based or cash-based awards to key employees. At December 31, 2015, performance shares and restricted stock were outstanding and 3.8 million shares of Alliant Energy’s common stock remained available for grants under the Amended and Restated OIP. Alliant Energy satisfies share payouts related to equity awards under the Amended and Restated OIP through the issuance of new shares of its common stock. Alliant Energy also has the DLIP, which permits the grant of cash-based long-term performance-based awards, including performance units and restricted cash awards, to certain key employees. At December 31, 2015, performance units and performance-contingent cash awards were outstanding under the DLIP. There is no limit to the number of grants that can be made under the DLIP and Alliant Energy satisfies all payouts under the DLIP through cash payments. A summary of compensation expense (including amounts allocated to IPL and WPL) and the related income tax benefits recognized for share-based compensation awards was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Compensation expense |  | $10.7 |  |  |  | $15.3 |  |  |  | $12.0 |  |  |  | $5.7 |  |  |  | $8.3 |  |  |  | $6.2 |  |  |  | $4.7 |  |  |  | $6.4 |  |  |  | $5.2 |
Income tax benefits | 4.4 |  |  | 6.2 |  |  | 4.8 |  |  | 2.4 |  |  | 3.4 |  |  | 2.5 |  |  | 1.9 |  |  | 2.6 |  |  | 2.1 |
As of December 31, 2015, total unrecognized compensation cost related to share-based compensation awards was $3.9 million, which is expected to be recognized over a weighted average period of between 1 and 2 years. Share-based compensation expense is recognized on a straight-line basis over the requisite service periods and is primarily recorded in “Other operation and maintenance” in the income statements. Performance Shares and Units - Payouts of performance shares and units to key employees are contingent upon achievement over 3-year periods of specified performance criteria, which currently include metrics of total shareowner return relative to an investor-owned utility peer group. Payouts of nonvested performance shares and units are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of performance shares and units to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested performance shares and units are forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. Nonvested performance shares and units do not have non-forfeitable rights to dividends when dividends are paid to common shareowners. Alliant Energy assumes it will make future payouts of its performance shares and units in cash; therefore, performance shares and units are accounted for as liability awards. Performance Shares - Performance shares can be paid out in shares of Alliant Energy’s common stock, cash or a combination of cash and stock. Each performance share’s value is based on the closing market price of one share of Alliant Energy’s common stock at the end of the performance period. The actual number of shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares. A summary of the performance shares activity, with share amounts representing the target number of performance shares, was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested shares, January 1 | 144,424 |  |  | 139,940 |  |  | 145,277 |
Granted | 45,403 |  |  | 51,221 |  |  | 49,093 |
Vested | (45,612 | ) |  | (45,235 | ) |  | (54,430 | )
Forfeited | — |  |  | (1,502 | ) |  | — |
Nonvested shares, December 31 | 144,215 |  |  | 144,424 |  |  | 139,940 |
Certain performance shares vested, resulting in payouts (a combination of cash and common stock) as follows:
| 2015 |  | 2014 |  | 2013
| 2012 Grant |  | 2011 Grant |  | 2010 Grant
Performance shares vested | 45,612 |  |  | 45,235 |  |  | 54,430 |
Percentage of target number of performance shares | 167.5 | % |  | 147.5 | % |  | 197.5 | %
Aggregate payout value (in millions) |  | $5.1 |  |  |  | $3.4 |  |  |  | $4.8 |
Payout - cash (in millions) |  | $3.2 |  |  |  | $2.9 |  |  |  | $4.4 |
Payout - common stock shares issued | 10,975 |  |  | 4,810 |  |  | 4,177 |
Performance Units - Performance units must be paid out in cash. Each performance unit’s value is based on the average price of one share of Alliant Energy’s common stock on the grant date of the award. The actual payout for performance units is dependent upon actual performance and may range from zero to 200% of the target number of units. A summary of the performance unit activity, with amounts representing the target number of performance units, was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested units, January 1 | 63,665 |  |  | 65,912 |  |  | 64,969 |
Granted | 17,837 |  |  | 20,422 |  |  | 22,201 |
Vested | (22,845 | ) |  | (20,751 | ) |  | (19,760 | )
Forfeited | (451 | ) |  | (1,918 | ) |  | (1,498 | )
Nonvested units, December 31 | 58,206 |  |  | 63,665 |  |  | 65,912 |
Certain performance units vested, resulting in cash payouts as follows:
| 2015 |  | 2014 |  | 2013
| 2012 Grant |  | 2011 Grant |  | 2010 Grant
Performance units vested | 22,845 |  |  | 20,751 |  |  | 19,760 |
Percentage of target number of performance units | 167.5 | % |  | 147.5 | % |  | 197.5 | %
Payout value (in millions) |  | $1.6 |  |  |  | $1.2 |  |  |  | $1.3 |
Fair Value of Awards - Information related to fair values of nonvested performance shares and units at December 31, 2015, by year of grant, were as follows:
| Performance Shares |  | Performance Units
| 2015 Grant |  | 2014 Grant |  | 2013 Grant |  | 2015 Grant |  | 2014 Grant |  | 2013 Grant
Nonvested awards | 45,403 |  |  | 49,719 |  |  | 49,093 |  |  | 17,386 |  |  | 19,440 |  |  | 21,380 |
Alliant Energy common stock closing price on December 31, 2015 |  | $62.45 |  |  |  | $62.45 |  |  |  | $62.45 |  |  |  |  |  |  |
Alliant Energy common stock closing price on grant date |  |  |  |  |  |  |  | $65.09 |  |  |  | $53.77 |  |  |  | $47.58 |
Estimated payout percentage based on performance criteria | 80 | % |  | 125 | % |  | 165 | % |  | 80 | % |  | 125 | % |  | 165 | %
Fair values of each nonvested award |  | $49.96 |  |  |  | $78.06 |  |  |  | $103.04 |  |  |  | $52.07 |  |  |  | $67.21 |  |  |  | $78.51 |
At December 31, 2015, fair values of nonvested performance shares and units were calculated based on Alliant Energy’s stock price and anticipated total shareowner returns of Alliant Energy and its investor-owned utility peer group over the performance period. The portion of the fair values based on anticipated total shareowner returns was estimated using a model that incorporates the probability of meeting performance targets based on historical returns relative to the peer group. Performance-Contingent Restricted Stock - Vesting of performance-contingent restricted stock grants are based on the achievement of certain performance targets (currently specified growth of consolidated income from continuing operations). If performance targets are not met within the performance period, which currently ranges from two to four years, these restricted stock grants are forfeited. Payouts of nonvested performance-contingent restricted stock are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of performance-contingent restricted stock to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested performance-contingent restricted stock is forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. The fair value of performance-contingent restricted stock is based on the closing market price on the grant date. A summary of the performance-contingent restricted stock activity was as follows:
| 2015 |  | 2014 |  | 2013
| Shares |  | Weighted Average Fair Value |  | Shares |  | Weighted Average Fair Value |  | Shares |  | Weighted Average Fair Value
Nonvested shares, January 1 | 98,812 |  |  |  | $50.69 |  |  | 158,922 |  |  |  | $42.71 |  |  | 211,651 |  |  |  | $32.42 |
Granted | 45,403 |  |  | 65.09 |  |  | 51,221 |  |  | 53.77 |  |  | 49,093 |  |  | 47.58 |
Vested (a) | (49,093 | ) |  | 47.58 |  |  | (90,847 | ) |  | 40.91 |  |  | — |  |  | — |
Forfeited (b) | — |  |  | — |  |  | (20,484 | ) |  | 39.85 |  |  | (101,822 | ) |  | 23.67 |
Nonvested shares, December 31 | 95,122 |  |  | 59.17 |  |  | 98,812 |  |  | 50.69 |  |  | 158,922 |  |  | 42.71 |
(a) | In 2015, 49,093 performance-contingent restricted shares granted in 2013 vested because the specified performance criteria for such shares were met. In 2014, 45,612 and 45,235 performance-contingent restricted shares granted in 2012 and 2011, respectively, vested because the specified performance criteria for such shares were met.
(b) | In 2013, 101,822 performance-contingent restricted shares granted in 2009 were forfeited because the specified performance criteria for such shares were not met. The forfeitures during 2014 were primarily caused by retirements and terminations of participants.
Performance-Contingent Cash Awards - Performance-contingent cash award payouts to key employees are based on the achievement of certain performance targets (currently specified growth of consolidated income from continuing operations). If performance targets are not met within the performance period, which currently ranges from two to four years, there are no payouts for these awards. Payouts of nonvested awards are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of these awards to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested awards are forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. Each performance-contingent cash award’s value is based on the price of one share of Alliant Energy’s common stock at the end of the performance period. Alliant Energy accounts for performance-contingent cash awards as liability awards because payouts will be made in the form of cash. A summary of the performance-contingent cash awards activity was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested awards, January 1 | 78,930 |  |  | 96,977 |  |  | 59,639 |
Granted | 41,105 |  |  | 42,446 |  |  | 39,530 |
Vested (a) | (37,332 | ) |  | (55,517 | ) |  | — |
Forfeited | (827 | ) |  | (4,976 | ) |  | (2,192 | )
Nonvested awards, December 31 | 81,876 |  |  | 78,930 |  |  | 96,977 |
(a) | In 2015, 37,332 performance-contingent cash awards granted in 2013 vested, resulting in cash payouts valued at $2.4 million. In 2014, 34,766 and 20,751 performance-contingent cash awards granted in 2012 and 2011 vested, resulting in cash payouts valued at $1.9 million and $1.1 million, respectively.
(c) Deferred Compensation Plan - Alliant Energy maintains a DCP under which key employees may defer up to 100% of base salary and performance-based compensation and directors may elect to defer all or part of their retainer and committee fees. Key employees who have made the maximum allowed contribution to the Alliant Energy 401(k) Savings Plan may receive an additional credit to the DCP. Key employees and directors may elect to have their deferrals credited to a company stock account, an interest account or equity accounts based on certain benchmark funds. Company Stock Accounts - The DCP does not permit diversification of deferrals credited to the company stock account and all distributions from participants’ company stock accounts are made in the form of shares of Alliant Energy common stock. The deferred compensation obligations for participants’ company stock accounts are recorded in “Additional paid-in capital” and the shares of Alliant Energy common stock held in a rabbi trust to satisfy this obligation are recorded in “Shares in deferred compensation trust” on Alliant Energy’s balance sheets. At December 31, the carrying value of the deferred compensation obligation for the company stock accounts and the shares in the deferred compensation trust based on the historical value of the shares of Alliant Energy common stock contributed to the rabbi trust, and the fair market value of the shares held in the rabbi trust were as follows (in millions):
| 2015 |  | 2014
Carrying value |  | $8.5 |  |  |  | $8.9 |
Fair market value | 13.4 |  |  | 15.9 |
Interest and Equity Accounts - Distributions from participants’ interest and equity accounts are in the form of cash payments. The deferred compensation obligations for participants’ interest and equity accounts are recorded in “Pension and other benefit obligations” on Alliant Energy’s and IPL’s balance sheets. At December 31, the carrying value of deferred compensation obligations for participants’ interest and equity accounts, which approximates fair market value, was as follows (in millions):
| Alliant Energy |  | IPL
| 2015 |  | 2014 |  | 2015 |  | 2014
Carrying value | $18.3 |  | $17.8 |  | $5.0 |  | $5.2
IPL [Member] |
Benefit Plans | BENEFIT PLANS (a) Pension and Other Postretirement Benefits Plans - Retirement benefits are provided to substantially all employees through various qualified and non-qualified non-contributory defined benefit pension plans, and/or through defined contribution plans (including 401(k) savings plans). Qualified and non-qualified non-contributory defined benefit pension plans are currently closed to new hires. Benefits of the non-contributory defined benefit pension plans are based on the plan participant’s years of service, age and compensation. Benefits of the defined contribution plans are based on the plan participant’s years of service, age, compensation and contributions. Certain defined benefit postretirement health care and life benefits are provided to eligible retirees. In general, the retiree health care plans consist of fixed benefit subsidy structures and the retiree life insurance plans are non-contributory. IPL and WPL account for their participation in Alliant Energy and Corporate Services sponsored plans as multiple-employer plans. Assumptions - The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows:
| Defined Benefit Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.47% |  | 4.18% |  | 4.97% |  | 4.30% |  | 3.97% |  | 4.59%
Discount rate for net periodic cost | 4.18% |  | 4.97% |  | 4.11% |  | 3.97% |  | 4.59% |  | 3.82%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 6.20% |  | 7.40% |  | 7.40%
Rate of compensation increase | 3.65 | % | - | 4.50% |  | 3.50 | % | - | 4.50% |  | 3.50 | % | - | 4.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
| Qualified Defined Benefit Pension Plan |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.50% |  | 4.20% |  | 5.05% |  | 4.28% |  | 3.94% |  | 4.55%
Discount rate for net periodic cost | 4.20% |  | 5.05% |  | 4.20% |  | 3.94% |  | 4.55% |  | 3.76%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 6.60% |  | 7.60% |  | 7.50%
Rate of compensation increase | 3.65% |  | 3.50% |  | 3.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
| Qualified Defined Benefit Pension Plan |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.51% |  | 4.20% |  | 5.05% |  | 4.28% |  | 3.96% |  | 4.56%
Discount rate for net periodic cost | 4.20% |  | 5.05% |  | 4.20% |  | 3.96% |  | 4.56% |  | 3.81%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 4.60% |  | 7.30% |  | 7.20%
Rate of compensation increase | 3.65% |  | 3.50% |  | 3.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
Expected rate of return on plan assets - The expected rate of return on plan assets is determined by analysis of projected asset class returns based on the target asset class allocations. A forward-looking building blocks approach is used, and historical returns, survey information and capital market information are reviewed to support the expected rate of return on plan assets assumption. Refer to “Investment Policy and Strategy for Plan Assets” below for additional information related to investment policy, and strategy and mix of assets for the pension and OPEB plans. Life Expectancy - The life expectancy assumption is used in determining the benefit obligation and net periodic benefit cost for defined benefit pension and OPEB plans. This assumption was updated as of December 31, 2014 and 2015 to utilize new mortality tables that were released in 2014 by the Society of Actuaries and updated in 2015, respectively. Net Periodic Benefit Costs (Credits) - The components of net periodic benefit costs (credits) for sponsored defined benefit pension and OPEB plans are included in the tables below (in millions). In IPL’s and WPL’s tables below, the defined benefit pension plans costs represent those respective costs for their bargaining unit employees covered under the qualified plans that they sponsor, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In IPL’s and WPL’s tables below, the OPEB plans costs (credits) represent respective costs (credits) for their employees, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Corporate Services sponsored OPEB plan.
Alliant Energy | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $15.9 |  |  |  | $13.1 |  |  |  | $15.7 |  |  |  | $5.5 |  |  |  | $5.2 |  |  |  | $6.3 |
Interest cost | 53.6 |  |  | 54.1 |  |  | 49.0 |  |  | 9.1 |  |  | 9.5 |  |  | 8.5 |
Expected return on plan assets (a) | (75.0 | ) |  | (74.9 | ) |  | (74.0 | ) |  | (8.4 | ) |  | (8.3 | ) |  | (8.1 | )
Amortization of prior service cost (credit) (b) | (0.2 | ) |  | — |  |  | 0.2 |  |  | (11.3 | ) |  | (11.9 | ) |  | (11.9 | )
Amortization of actuarial loss (c) | 35.4 |  |  | 19.5 |  |  | 36.2 |  |  | 4.8 |  |  | 2.4 |  |  | 4.9 |
Additional benefit costs (d) | 0.5 |  |  | — |  |  | 9.0 |  |  | — |  |  | — |  |  | — |
|  | $30.2 |  |  |  | $11.8 |  |  |  | $36.1 |  |  |  | ($0.3 | ) |  |  | ($3.1 | ) |  |  | ($0.3 | )
IPL | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $8.8 |  |  |  | $7.2 |  |  |  | $8.6 |  |  |  | $2.4 |  |  |  | $2.4 |  |  |  | $2.9 |
Interest cost | 25.0 |  |  | 25.1 |  |  | 22.9 |  |  | 3.8 |  |  | 3.9 |  |  | 3.6 |
Expected return on plan assets (a) | (35.8 | ) |  | (35.7 | ) |  | (35.2 | ) |  | (5.7 | ) |  | (5.8 | ) |  | (5.6 | )
Amortization of prior service cost (credit) (b) | (0.1 | ) |  | — |  |  | 0.1 |  |  | (6.1 | ) |  | (6.3 | ) |  | (6.3 | )
Amortization of actuarial loss (c) | 15.3 |  |  | 8.0 |  |  | 15.2 |  |  | 2.3 |  |  | 1.1 |  |  | 2.7 |
Additional benefit costs (d) | — |  |  | — |  |  | 2.6 |  |  | — |  |  | — |  |  | — |
|  | $13.2 |  |  |  | $4.6 |  |  |  | $14.2 |  |  |  | ($3.3 | ) |  |  | ($4.7 | ) |  |  | ($2.7 | )
WPL | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $5.8 |  |  |  | $4.9 |  |  |  | $5.9 |  |  |  | $2.1 |  |  |  | $2.0 |  |  |  | $2.5 |
Interest cost | 22.6 |  |  | 22.6 |  |  | 20.7 |  |  | 3.7 |  |  | 3.8 |  |  | 3.4 |
Expected return on plan assets (a) | (32.4 | ) |  | (32.4 | ) |  | (31.9 | ) |  | (1.5 | ) |  | (1.3 | ) |  | (1.3 | )
Amortization of prior service cost (credit) (b) | 0.2 |  |  | 0.3 |  |  | 0.3 |  |  | (3.5 | ) |  | (3.9 | ) |  | (3.9 | )
Amortization of actuarial loss (c) | 16.8 |  |  | 9.2 |  |  | 17.1 |  |  | 2.2 |  |  | 1.3 |  |  | 1.9 |
Additional benefit costs (d) | 0.5 |  |  | — |  |  | 0.6 |  |  | — |  |  | — |  |  | — |
|  | $13.5 |  |  |  | $4.6 |  |  |  | $12.7 |  |  |  | $3.0 |  |  |  | $1.9 |  |  |  | $2.6 |
(a) | The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets.
(b) | Unrecognized prior service costs (credits) for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan.
(c) | Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Cash Balance Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits.
(d) | In 2013, Alliant Energy filed a stipulation agreement with the Western Wisconsin Court related to a class-action lawsuit against the Cash Balance Plan. As a result, Alliant Energy recognized $9.0 million of additional benefits costs in 2013 related to the agreement. IPL recognized $5.5 million ($2.6 million directly assigned and $2.9 million allocated by Corporate Services) and WPL recognized $2.8 million ($0.6 million directly assigned and $2.2 million allocated by Corporate Services) of additional benefits costs in 2013 related to the agreement.
The estimated amortization from “Regulatory assets” and “Regulatory liabilities” on the balance sheets and AOCL on Alliant Energy’s balance sheet into net periodic benefit cost in 2016 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Defined Benefit |  |  |  | Defined Benefit |  |  |  | Defined Benefit |  |
| Pension Plans |  | OPEB Plans |  | Pension Plans |  | OPEB Plans |  | Pension Plans |  | OPEB Plans
Actuarial loss |  | $37.4 |  |  |  | $4.8 |  |  |  | $16.5 |  |  |  | $2.6 |  |  |  | $17.6 |  |  |  | $1.8 |
Prior service cost (credit) | (0.3 | ) |  | (4.1 | ) |  | (0.2 | ) |  | (2.6 | ) |  | 0.2 |  |  | (0.9 | )
|  | $37.1 |  |  |  | $0.7 |  |  |  | $16.3 |  |  |  | $— |  |  |  | $17.8 |  |  |  | $0.9 |
Net periodic benefit costs are primarily included in “Other operation and maintenance” in the income statements. Benefit Plan Assets and Obligations - A reconciliation of the funded status of Alliant Energy’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on Alliant Energy’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $1,301.5 |  |  |  | $1,113.4 |  |  |  | $231.1 |  |  |  | $208.7 |
Service cost | 15.9 |  |  | 13.1 |  |  | 5.5 |  |  | 5.2 |
Interest cost | 53.6 |  |  | 54.1 |  |  | 9.1 |  |  | 9.5 |
Plan participants’ contributions | — |  |  | — |  |  | 3.1 |  |  | 2.8 |
Plan amendments | — |  |  | — |  |  | (0.3 | ) |  | — |
Additional benefit costs | 0.5 |  |  | — |  |  | — |  |  | — |
Actuarial (gain) loss | (70.1 | ) |  | 195.8 |  |  | (9.4 | ) |  | 22.3 |
Gross benefits paid | (95.1 | ) |  | (74.9 | ) |  | (17.7 | ) |  | (17.4 | )
Net benefit obligation at December 31 | 1,206.3 |  |  | 1,301.5 |  |  | 221.4 |  |  | 231.1 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 1,018.1 |  |  | 1,022.9 |  |  | 121.6 |  |  | 124.9 |
Actual return on plan assets | (30.2 | ) |  | 66.4 |  |  | (4.9 | ) |  | 5.6 |
Employer contributions | 2.2 |  |  | 3.7 |  |  | 4.8 |  |  | 5.7 |
Plan participants’ contributions | — |  |  | — |  |  | 3.1 |  |  | 2.8 |
Gross benefits paid | (95.1 | ) |  | (74.9 | ) |  | (17.7 | ) |  | (17.4 | )
Fair value of plan assets at December 31 | 895.0 |  |  | 1,018.1 |  |  | 106.9 |  |  | 121.6 |
Under funded status at December 31 |  | ($311.3 | ) |  |  | ($283.4 | ) |  |  | ($114.5 | ) |  |  | ($109.5 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $3.0 |  |  |  | $6.1 |
Other current liabilities | (2.6 | ) |  | (2.5 | ) |  | (6.2 | ) |  | (5.6 | )
Pension and other benefit obligations | (308.7 | ) |  | (280.9 | ) |  | (111.3 | ) |  | (110.0 | )
Net amounts recognized at December 31 |  | ($311.3 | ) |  |  | ($283.4 | ) |  |  | ($114.5 | ) |  |  | ($109.5 | )
Amounts recognized in Regulatory Assets and AOCL consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $533.1 |  |  |  | $533.4 |  |  |  | $59.8 |  |  |  | $60.7 |
Prior service credit | (7.2 | ) |  | (7.4 | ) |  | (5.6 | ) |  | (16.7 | )
|  | $525.9 |  |  |  | $526.0 |  |  |  | $54.2 |  |  |  | $44.0 |
(a) | Refer to Note 2 and Alliant Energy’s common equity statements for amounts recognized in “Regulatory assets” and “AOCL,” respectively, on Alliant Energy’s balance sheets.
In IPL’s and WPL’s tables below, the defined benefit pension plans amounts represent those respective amounts for their bargaining unit employees covered under the qualified plans that they sponsor, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In IPL’s and WPL’s tables below, the OPEB plans amounts represent respective amounts for their employees, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Corporate Services sponsored OPEB plan. A reconciliation of the funded status of IPL’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on IPL’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $603.1 |  |  |  | $514.0 |  |  |  | $96.4 |  |  |  | $87.8 |
Service cost | 8.8 |  |  | 7.2 |  |  | 2.4 |  |  | 2.4 |
Interest cost | 25.0 |  |  | 25.1 |  |  | 3.8 |  |  | 3.9 |
Plan participants’ contributions | — |  |  | — |  |  | 1.0 |  |  | 0.9 |
Plan amendments | — |  |  | — |  |  | (0.1 | ) |  | — |
Actuarial (gain) loss | (32.3 | ) |  | 91.4 |  |  | (4.6 | ) |  | 8.6 |
Gross benefits paid | (48.5 | ) |  | (34.6 | ) |  | (7.6 | ) |  | (7.2 | )
Net benefit obligation at December 31 | 556.1 |  |  | 603.1 |  |  | 91.3 |  |  | 96.4 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 484.7 |  |  | 485.9 |  |  | 78.7 |  |  | 81.2 |
Actual return on plan assets | (14.3 | ) |  | 32.1 |  |  | (3.1 | ) |  | 3.6 |
Employer contributions | 0.8 |  |  | 1.3 |  |  | 0.2 |  |  | 0.2 |
Plan participants’ contributions | — |  |  | — |  |  | 1.0 |  |  | 0.9 |
Gross benefits paid | (48.5 | ) |  | (34.6 | ) |  | (7.6 | ) |  | (7.2 | )
Fair value of plan assets at December 31 | 422.7 |  |  | 484.7 |  |  | 69.2 |  |  | 78.7 |
Under funded status at December 31 |  | ($133.4 | ) |  |  | ($118.4 | ) |  |  | ($22.1 | ) |  |  | ($17.7 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $— |  |  |  | $1.2 |
Other current liabilities | (0.8 | ) |  | (0.8 | ) |  | — |  |  | — |
Pension and other benefit obligations | (132.6 | ) |  | (117.6 | ) |  | (22.1 | ) |  | (18.9 | )
Net amounts recognized at December 31 |  | ($133.4 | ) |  |  | ($118.4 | ) |  |  | ($22.1 | ) |  |  | ($17.7 | )
Amounts recognized in Regulatory Assets consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $235.5 |  |  |  | $233.1 |  |  |  | $29.8 |  |  |  | $27.9 |
Prior service credit | (2.5 | ) |  | (2.6 | ) |  | (2.7 | ) |  | (8.7 | )
|  | $233.0 |  |  |  | $230.5 |  |  |  | $27.1 |  |  |  | $19.2 |
(a) | Refer to Note 2 for amounts recognized in “Regulatory assets” on IPL’s balance sheets.
A reconciliation of the funded status of WPL’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on WPL’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $547.6 |  |  |  | $460.8 |  |  |  | $94.0 |  |  |  | $85.6 |
Service cost | 5.8 |  |  | 4.9 |  |  | 2.1 |  |  | 2.0 |
Interest cost | 22.6 |  |  | 22.6 |  |  | 3.7 |  |  | 3.8 |
Plan participants’ contributions | — |  |  | — |  |  | 1.6 |  |  | 1.3 |
Plan amendments | — |  |  | — |  |  | (0.2 | ) |  | — |
Additional benefit costs | 0.5 |  |  | — |  |  | — |  |  | — |
Actuarial (gain) loss | (30.0 | ) |  | 86.7 |  |  | (3.5 | ) |  | 9.2 |
Gross benefits paid | (40.6 | ) |  | (27.4 | ) |  | (8.0 | ) |  | (7.9 | )
Net benefit obligation at December 31 | 505.9 |  |  | 547.6 |  |  | 89.7 |  |  | 94.0 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 440.3 |  |  | 438.8 |  |  | 21.8 |  |  | 21.7 |
Actual return on plan assets | (13.0 | ) |  | 28.6 |  |  | (1.1 | ) |  | 1.2 |
Employer contributions | 0.1 |  |  | 0.3 |  |  | 4.4 |  |  | 5.5 |
Plan participants’ contributions | — |  |  | — |  |  | 1.6 |  |  | 1.3 |
Gross benefits paid | (40.6 | ) |  | (27.4 | ) |  | (8.0 | ) |  | (7.9 | )
Fair value of plan assets at December 31 | 386.8 |  |  | 440.3 |  |  | 18.7 |  |  | 21.8 |
Under funded status at December 31 |  | ($119.1 | ) |  |  | ($107.3 | ) |  |  | ($71.0 | ) |  |  | ($72.2 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $3.0 |  |  |  | $4.9 |
Other current liabilities | (0.1 | ) |  | (0.1 | ) |  | (6.0 | ) |  | (5.5 | )
Pension and other benefit obligations | (119.0 | ) |  | (107.2 | ) |  | (68.0 | ) |  | (71.6 | )
Net amounts recognized at December 31 |  | ($119.1 | ) |  |  | ($107.3 | ) |  |  | ($71.0 | ) |  |  | ($72.2 | )
Amounts recognized in Regulatory Assets consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $232.1 |  |  |  | $233.5 |  |  |  | $23.3 |  |  |  | $26.3 |
Prior service credit | (1.2 | ) |  | (1.0 | ) |  | (2.4 | ) |  | (5.6 | )
|  | $230.9 |  |  |  | $232.5 |  |  |  | $20.9 |  |  |  | $20.7 |
(a) | Refer to Note 2 for amounts recognized in “Regulatory assets” on WPL’s balance sheets.
Included in the following tables are accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $1,166.0 |  |  |  | $1,255.0 |  |  |  | $221.4 |  |  |  | $231.1 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 1,166.0 |  |  | 1,255.0 |  |  | 221.4 |  |  | 231.1 |
Fair value of plan assets | 895.0 |  |  | 1,018.1 |  |  | 106.9 |  |  | 121.6 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 1,206.3 |  |  | 1,301.5 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 895.0 |  |  | 1,018.1 |  |  | N/A |  |  | N/A |
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $531.0 |  |  |  | $575.5 |  |  |  | $91.3 |  |  |  | $96.4 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 531.0 |  |  | 575.5 |  |  | 91.3 |  |  | 96.4 |
Fair value of plan assets | 422.7 |  |  | 484.7 |  |  | 69.2 |  |  | 78.7 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 556.1 |  |  | 603.1 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 422.7 |  |  | 484.7 |  |  | N/A |  |  | N/A |
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $493.8 |  |  |  | $532.5 |  |  |  | $89.7 |  |  |  | $94.0 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 493.8 |  |  | 532.5 |  |  | 89.7 |  |  | 94.0 |
Fair value of plan assets | 386.8 |  |  | 440.3 |  |  | 18.7 |  |  | 21.8 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 505.9 |  |  | 547.6 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 386.8 |  |  | 440.3 |  |  | N/A |  |  | N/A |
In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions):
| IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014
Regulatory assets |  | $38.0 |  |  |  | $38.2 |  |  |  | $29.5 |  |  |  | $28.0 |
Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2016 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Defined benefit pension plans (a) |  | $2.6 |  |  |  | $0.8 |  |  |  | $0.1 |
OPEB plans | 5.8 |  |  | — |  |  | 5.5 |
(a) | Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans.
Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions):
Alliant Energy | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $69.5 |  |  |  | $74.3 |  |  |  | $72.8 |  |  |  | $74.3 |  |  |  | $78.7 |  |  |  | $401.4 |
OPEB | 17.8 |  |  | 18.1 |  |  | 18.2 |  |  | 18.3 |  |  | 18.2 |  |  | 86.9 |
|  | $87.3 |  |  |  | $92.4 |  |  |  | $91.0 |  |  |  | $92.6 |  |  |  | $96.9 |  |  |  | $488.3 |
IPL | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $32.8 |  |  |  | $34.1 |  |  |  | $34.8 |  |  |  | $34.6 |  |  |  | $37.8 |  |  |  | $190.8 |
OPEB | 7.6 |  |  | 7.6 |  |  | 7.6 |  |  | 7.5 |  |  | 7.6 |  |  | 36.0 |
|  | $40.4 |  |  |  | $41.7 |  |  |  | $42.4 |  |  |  | $42.1 |  |  |  | $45.4 |  |  |  | $226.8 |
WPL | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $29.1 |  |  |  | $29.8 |  |  |  | $30.7 |  |  |  | $31.1 |  |  |  | $32.2 |  |  |  | $163.7 |
OPEB | 7.5 |  |  | 7.8 |  |  | 7.8 |  |  | 7.8 |  |  | 7.6 |  |  | 34.7 |
|  | $36.6 |  |  |  | $37.6 |  |  |  | $38.5 |  |  |  | $38.9 |  |  |  | $39.8 |  |  |  | $198.4 |
Investment Policy and Strategy for Plan Assets - Investment policies and strategies employed with respect to assets of defined benefit pension and OPEB plans are to combine both preservation of principal and prudent and reasonable risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term. It is recognized that risk and volatility are present with all types of investments. However, risk is mitigated at the total fund level through diversification by asset class including U.S. and international equity and fixed income exposure, global asset and risk parity strategies, the number of individual investments, and sector and industry limits. Global asset and risk parity strategies include investments in global equity, global debt, commodities and currencies. Defined Benefit Pension Plan Assets - For assets of defined benefit pension plans, the mix among asset classes is controlled by asset allocation targets. Historical performance results and future expectations suggest that equity securities will provide higher total investment returns than debt securities over a long-term investment horizon. Consistent with the goals of meeting obligations to plan participants and minimizing benefit costs over the long-term, the defined benefit pension plans have a long-term investment posture more heavily weighted towards equity holdings. The asset allocation is monitored regularly and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. An overlay management service is also used to help maintain target allocations and meet liquidity needs. The overlay manager is authorized to use derivative financial instruments to facilitate this service. For separately managed accounts, prohibited investment vehicles include, but may not be limited to, direct ownership of real estate, margin trading, oil and gas limited partnerships and securities of the managers’ firms or affiliate firms. At December 31, 2015, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows:
| Target Range |  | Actual
| Allocation |  | Allocation
Cash and equivalents | 0 | % | - | 5% |  | 2%
Equity securities: |  |  |  |  |
U.S. large cap core | 8 | % | - | 18% |  | 11%
U.S. large cap value | 2.5 | % | - | 12.5% |  | 7%
U.S. large cap growth | 2.5 | % | - | 12.5% |  | 7%
U.S. small cap value | 0 | % | - | 4% |  | 1%
U.S. small cap growth | 0 | % | - | 4% |  | 2%
International - developed markets | 7 | % | - | 19% |  | 12%
International - emerging markets | 0 | % | - | 10% |  | 5%
Global asset allocation securities | 5 | % | - | 15% |  | 11%
Risk parity allocation securities | 5 | % | - | 15% |  | 10%
Fixed income securities | 20 | % | - | 40% |  | 32%
Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts. The investment policy and strategy of the 401(h) assets, except for the WPL 401(h) assets, mirrors those of the defined benefit pension plans, which are discussed above. For VEBA trusts with assets greater than $5 million and the WPL 401(h) assets, the mix among asset classes is controlled by allocation targets. The asset allocation is monitored regularly and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. Mutual funds are used to achieve the desired diversification. At December 31, 2015, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows:
| Target Range |  | Actual
| Allocation |  | Allocation
Cash and equivalents | 0 | % | - | 15% |  | 3%
Equity securities: |  |  |  |  |
Domestic | 0 | % | - | 45% |  | 21%
International | 0 | % | - | 21% |  | 13%
Global asset allocation securities | 5 | % | - | 40% |  | 16%
Fixed income securities | 10 | % | - | 70% |  | 47%
Fair Value Measurements - The following tables report a framework for measuring fair value. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy and examples of each are as follows: Level 1 - Pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. Investments in securities held in registered investment companies and directly held equity securities are valued at the closing price reported in the active market in which the securities are traded. Level 2 - Pricing inputs are quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability and inputs that are derived principally from or corroborated by observable market data by correlation or other means. Investments in common/collective trusts are valued at the net asset value of shares held by the plans, which is based on the fair market value of the underlying investments in the common/collective trusts. Investments in corporate bonds are valued at the closing price reported in the active market for similar assets in which the individual securities are traded or based on yields currently available on comparable securities of issuers with similar credit ratings. Level 3 - Pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while Alliant Energy, IPL and WPL believe their valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date. At December 31, the fair values of Alliant Energy’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $23.1 |  |  |  | $— |  |  |  | $23.1 |  |  |  | $— |  |  |  | $49.3 |  |  |  | $— |  |  |  | $49.3 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 100.4 |  |  | 100.4 |  |  | — |  |  | — |  |  | 137.2 |  |  | 137.2 |  |  | — |  |  | — |
U.S. large cap value | 59.9 |  |  | — |  |  | 59.9 |  |  | — |  |  | 72.2 |  |  | — |  |  | 72.2 |  |  | — |
U.S. large cap growth | 60.5 |  |  | — |  |  | 60.5 |  |  | — |  |  | 73.2 |  |  | — |  |  | 73.2 |  |  | — |
U.S. small cap value | 14.2 |  |  | — |  |  | 14.2 |  |  | — |  |  | 15.2 |  |  | — |  |  | 15.2 |  |  | — |
U.S. small cap growth | 16.0 |  |  | 16.0 |  |  | — |  |  | — |  |  | 15.9 |  |  | 15.9 |  |  | — |  |  | — |
International - developed markets | 104.4 |  |  | 52.7 |  |  | 51.7 |  |  | — |  |  | 102.9 |  |  | 52.1 |  |  | 50.8 |  |  | — |
International - emerging markets | 41.2 |  |  | 41.2 |  |  | — |  |  | — |  |  | 47.2 |  |  | 47.2 |  |  | — |  |  | — |
Global asset allocation securities | 96.3 |  |  | 52.9 |  |  | 43.4 |  |  | — |  |  | 99.9 |  |  | 57.2 |  |  | 42.7 |  |  | — |
Risk parity allocation securities | 94.0 |  |  | — |  |  | 94.0 |  |  | — |  |  | 102.5 |  |  | — |  |  | 102.5 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.1 |  |  | — |
Fixed income funds | 284.8 |  |  | — |  |  | 284.8 |  |  | — |  |  | 302.7 |  |  | 0.2 |  |  | 302.5 |  |  | — |
| 894.8 |  |  |  | $263.2 |  |  |  | $631.6 |  |  |  | $— |  |  | 1,018.3 |  |  |  | $309.8 |  |  |  | $708.5 |  |  |  | $— |
Accrued investment income | 0.2 |  |  |  |  |  |  |  |  | 0.1 |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.3 | ) |  |  |  |  |  |
Total pension plan assets |  | $895.0 |  |  |  |  |  |  |  |  |  | $1,018.1 |  |  |  |  |  |  |
At December 31, the fair values of IPL’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $10.9 |  |  |  | $— |  |  |  | $10.9 |  |  |  | $— |  |  |  | $23.5 |  |  |  | $— |  |  |  | $23.5 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 47.4 |  |  | 47.4 |  |  | — |  |  | — |  |  | 65.3 |  |  | 65.3 |  |  | — |  |  | — |
U.S. large cap value | 28.3 |  |  | — |  |  | 28.3 |  |  | — |  |  | 34.4 |  |  | — |  |  | 34.4 |  |  | — |
U.S. large cap growth | 28.6 |  |  | — |  |  | 28.6 |  |  | — |  |  | 34.9 |  |  | — |  |  | 34.9 |  |  | — |
U.S. small cap value | 6.7 |  |  | — |  |  | 6.7 |  |  | — |  |  | 7.2 |  |  | — |  |  | 7.2 |  |  | — |
U.S. small cap growth | 7.5 |  |  | 7.5 |  |  | — |  |  | — |  |  | 7.6 |  |  | 7.6 |  |  | — |  |  | — |
International - developed markets | 49.3 |  |  | 24.9 |  |  | 24.4 |  |  | — |  |  | 49.0 |  |  | 24.8 |  |  | 24.2 |  |  | — |
International - emerging markets | 19.5 |  |  | 19.5 |  |  | — |  |  | — |  |  | 22.5 |  |  | 22.5 |  |  | — |  |  | — |
Global asset allocation securities | 45.5 |  |  | 25.0 |  |  | 20.5 |  |  | — |  |  | 47.5 |  |  | 27.2 |  |  | 20.3 |  |  | — |
Risk parity allocation securities | 44.4 |  |  | — |  |  | 44.4 |  |  | — |  |  | 48.8 |  |  | — |  |  | 48.8 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 134.5 |  |  | — |  |  | 134.5 |  |  | — |  |  | 144.1 |  |  | 0.1 |  |  | 144.0 |  |  | — |
| 422.6 |  |  |  | $124.3 |  |  |  | $298.3 |  |  |  | $— |  |  | 484.8 |  |  |  | $147.5 |  |  |  | $337.3 |  |  |  | $— |
Accrued investment income | 0.1 |  |  |  |  |  |  |  |  | 0.1 |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.2 | ) |  |  |  |  |  |
Total pension plan assets |  | $422.7 |  |  |  |  |  |  |  |  |  | $484.7 |  |  |  |  |  |  |
At December 31, the fair values of WPL’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $10.0 |  |  |  | $— |  |  |  | $10.0 |  |  |  | $— |  |  |  | $21.3 |  |  |  | $— |  |  |  | $21.3 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 43.4 |  |  | 43.4 |  |  | — |  |  | — |  |  | 59.3 |  |  | 59.3 |  |  | — |  |  | — |
U.S. large cap value | 25.9 |  |  | — |  |  | 25.9 |  |  | — |  |  | 31.3 |  |  | — |  |  | 31.3 |  |  | — |
U.S. large cap growth | 26.2 |  |  | — |  |  | 26.2 |  |  | — |  |  | 31.7 |  |  | — |  |  | 31.7 |  |  | — |
U.S. small cap value | 6.1 |  |  | — |  |  | 6.1 |  |  | — |  |  | 6.6 |  |  | — |  |  | 6.6 |  |  | — |
U.S. small cap growth | 6.9 |  |  | 6.9 |  |  | — |  |  | — |  |  | 6.9 |  |  | 6.9 |  |  | — |  |  | — |
International - developed markets | 45.1 |  |  | 22.8 |  |  | 22.3 |  |  | — |  |  | 44.5 |  |  | 22.5 |  |  | 22.0 |  |  | — |
International - emerging markets | 17.8 |  |  | 17.8 |  |  | — |  |  | — |  |  | 20.4 |  |  | 20.4 |  |  | — |  |  | — |
Global asset allocation securities | 41.6 |  |  | 22.8 |  |  | 18.8 |  |  | — |  |  | 43.2 |  |  | 24.8 |  |  | 18.4 |  |  | — |
Risk parity allocation securities | 40.6 |  |  | — |  |  | 40.6 |  |  | — |  |  | 44.3 |  |  | — |  |  | 44.3 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 123.1 |  |  | — |  |  | 123.1 |  |  | — |  |  | 130.9 |  |  | 0.1 |  |  | 130.8 |  |  | — |
| 386.7 |  |  |  | $113.7 |  |  |  | $273.0 |  |  |  | $— |  |  | 440.4 |  |  |  | $134.0 |  |  |  | $306.4 |  |  |  | $— |
Accrued investment income | 0.1 |  |  |  |  |  |  |  |  | — |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.1 | ) |  |  |  |  |  |
Total pension plan assets |  | $386.8 |  |  |  |  |  |  |  |  |  | $440.3 |  |  |  |  |  |  |
At December 31, the fair values of Alliant Energy’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $3.6 |  |  |  | $— |  |  |  | $3.6 |  |  |  | $— |  |  |  | $3.7 |  |  |  | $— |  |  |  | $3.7 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | 21.1 |  |  | 21.1 |  |  | — |  |  | — |  |  | 35.8 |  |  | 35.8 |  |  | — |  |  | — |
U.S. large cap core | 0.9 |  |  | 0.9 |  |  | — |  |  | — |  |  | 2.9 |  |  | 2.9 |  |  | — |  |  | — |
U.S. large cap value | 0.5 |  |  | — |  |  | 0.5 |  |  | — |  |  | 1.5 |  |  | — |  |  | 1.5 |  |  | — |
U.S. large cap growth | 0.5 |  |  | — |  |  | 0.5 |  |  | — |  |  | 1.6 |  |  | — |  |  | 1.6 |  |  | — |
U.S. small cap value | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. small cap growth | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.4 |  |  | 0.4 |  |  | — |  |  | — |
International - blend | 12.5 |  |  | 12.5 |  |  | — |  |  | — |  |  | 14.2 |  |  | 14.2 |  |  | — |  |  | — |
International - developed markets | 1.0 |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | 2.2 |  |  | 1.1 |  |  | 1.1 |  |  | — |
International - emerging markets | 0.4 |  |  | 0.4 |  |  | — |  |  | — |  |  | 1.0 |  |  | 1.0 |  |  | — |  |  | — |
Global asset allocation securities | 16.4 |  |  | 16.0 |  |  | 0.4 |  |  | — |  |  | 30.3 |  |  | 29.4 |  |  | 0.9 |  |  | — |
Risk parity allocation securities | 0.9 |  |  | — |  |  | 0.9 |  |  | — |  |  | 2.2 |  |  | — |  |  | 2.2 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 48.9 |  |  | 46.3 |  |  | 2.6 |  |  | — |  |  | 25.5 |  |  | 19.0 |  |  | 6.5 |  |  | — |
Total OPEB plan assets |  | $106.9 |  |  |  | $97.8 |  |  |  | $9.1 |  |  |  | $— |  |  |  | $121.6 |  |  |  | $103.8 |  |  |  | $17.8 |  |  |  | $— |
At December 31, the fair values of IPL’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $0.9 |  |  |  | $— |  |  |  | $0.9 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | 16.6 |  |  | 16.6 |  |  | — |  |  | — |  |  | 27.2 |  |  | 27.2 |  |  | — |  |  | — |
U.S. large cap core | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | — |
U.S. large cap value | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. large cap growth | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. small cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.1 |  |  | — |
U.S. small cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | 0.1 |  |  | — |  |  | — |
International - blend | 10.7 |  |  | 10.7 |  |  | — |  |  | — |  |  | 10.7 |  |  | 10.7 |  |  | — |  |  | — |
International - developed markets | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.4 |  |  | 0.2 |  |  | 0.2 |  |  | — |
International - emerging markets | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | 0.2 |  |  | — |  |  | — |
Global asset allocation securities | 6.9 |  |  | 6.9 |  |  | — |  |  | — |  |  | 21.6 |  |  | 21.5 |  |  | 0.1 |  |  | — |
Risk parity allocation securities | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.4 |  |  | — |  |  | 0.4 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 33.6 |  |  | 33.3 |  |  | 0.3 |  |  | — |  |  | 15.5 |  |  | 14.3 |  |  | 1.2 |  |  | — |
Total OPEB plan assets |  | $69.2 |  |  |  | $67.7 |  |  |  | $1.5 |  |  |  | $— |  |  |  | $78.7 |  |  |  | $74.7 |  |  |  | $4.0 |  |  |  | $— |
At December 31, the fair values of WPL’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $2.3 |  |  |  | $— |  |  |  | $2.3 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | — |  |  | — |  |  | — |  |  | — |  |  | 3.6 |  |  | 3.6 |  |  | — |  |  | — |
U.S. large cap core | — |  |  | — |  |  | — |  |  | — |  |  | 1.6 |  |  | 1.6 |  |  | — |  |  | — |
U.S. large cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.8 |  |  | — |  |  | 0.8 |  |  | — |
U.S. large cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.8 |  |  | — |  |  | 0.8 |  |  | — |
U.S. small cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | — |  |  | 0.2 |  |  | — |
U.S. small cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | 0.2 |  |  | — |  |  | — |
International - blend | — |  |  | — |  |  | — |  |  | — |  |  | 1.4 |  |  | 1.4 |  |  | — |  |  | — |
International - developed markets | — |  |  | — |  |  | — |  |  | — |  |  | 1.2 |  |  | 0.6 |  |  | 0.6 |  |  | — |
International - emerging markets | — |  |  | — |  |  | — |  |  | — |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | — |
Global asset allocation securities | 5.4 |  |  | 5.4 |  |  | — |  |  | — |  |  | 3.8 |  |  | 3.3 |  |  | 0.5 |  |  | — |
Risk parity allocation securities | — |  |  | — |  |  | — |  |  | — |  |  | 1.1 |  |  | — |  |  | 1.1 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 11.0 |  |  | 11.0 |  |  | — |  |  | — |  |  | 5.2 |  |  | 1.8 |  |  | 3.4 |  |  | — |
Total OPEB plan assets |  | $18.7 |  |  |  | $16.4 |  |  |  | $2.3 |  |  |  | $— |  |  |  | $21.8 |  |  |  | $13.0 |  |  |  | $8.8 |  |  |  | $— |
For the various defined benefit pension and OPEB plans, Alliant Energy common stock represented less than 1% of assets directly held in the plans at December 31, 2015 and 2014. 401(k) Savings Plans - A significant number of employees participate in defined contribution retirement plans (401(k) savings plans). Alliant Energy common stock represented 11.6% and 12.6% of total assets held in 401(k) savings plans at December 31, 2015 and 2014, respectively. Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  |  | 2014 |  |  | 2013 |  |  | 2015 |  | 2014 |  | 2013
401(k) costs |  | $24.9 |  |  |  | $22.5 |  |  |  | $19.2 |  |  |  | $12.7 |  |  |  | $11.1 |  |  |  | $9.9 |  |  |  | $11.2 |  |  |  | $10.5 |  |  |  | $8.5 |
Voluntary Employee Separation Charges - In 2015, Alliant Energy offered certain employees a voluntary separation package. Approximately 2% of total Alliant Energy employees accepted this package, which resulted in Alliant Energy, IPL and WPL recording charges of $8 million, $5 million and $3 million, respectively, in 2015. (b) Equity-based Compensation Plans - In 2015, Alliant Energy’s shareowners approved the Amended and Restated OIP, which permits the grant of shares of Alliant Energy common stock, restricted stock, restricted stock units, performance shares, performance units, and other stock-based or cash-based awards to key employees. At December 31, 2015, performance shares and restricted stock were outstanding and 3.8 million shares of Alliant Energy’s common stock remained available for grants under the Amended and Restated OIP. Alliant Energy satisfies share payouts related to equity awards under the Amended and Restated OIP through the issuance of new shares of its common stock. Alliant Energy also has the DLIP, which permits the grant of cash-based long-term performance-based awards, including performance units and restricted cash awards, to certain key employees. At December 31, 2015, performance units and performance-contingent cash awards were outstanding under the DLIP. There is no limit to the number of grants that can be made under the DLIP and Alliant Energy satisfies all payouts under the DLIP through cash payments. A summary of compensation expense (including amounts allocated to IPL and WPL) and the related income tax benefits recognized for share-based compensation awards was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Compensation expense |  | $10.7 |  |  |  | $15.3 |  |  |  | $12.0 |  |  |  | $5.7 |  |  |  | $8.3 |  |  |  | $6.2 |  |  |  | $4.7 |  |  |  | $6.4 |  |  |  | $5.2 |
Income tax benefits | 4.4 |  |  | 6.2 |  |  | 4.8 |  |  | 2.4 |  |  | 3.4 |  |  | 2.5 |  |  | 1.9 |  |  | 2.6 |  |  | 2.1 |
As of December 31, 2015, total unrecognized compensation cost related to share-based compensation awards was $3.9 million, which is expected to be recognized over a weighted average period of between 1 and 2 years. Share-based compensation expense is recognized on a straight-line basis over the requisite service periods and is primarily recorded in “Other operation and maintenance” in the income statements. Performance Shares and Units - Payouts of performance shares and units to key employees are contingent upon achievement over 3-year periods of specified performance criteria, which currently include metrics of total shareowner return relative to an investor-owned utility peer group. Payouts of nonvested performance shares and units are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of performance shares and units to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested performance shares and units are forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. Nonvested performance shares and units do not have non-forfeitable rights to dividends when dividends are paid to common shareowners. Alliant Energy assumes it will make future payouts of its performance shares and units in cash; therefore, performance shares and units are accounted for as liability awards. Performance Shares - Performance shares can be paid out in shares of Alliant Energy’s common stock, cash or a combination of cash and stock. Each performance share’s value is based on the closing market price of one share of Alliant Energy’s common stock at the end of the performance period. The actual number of shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares. A summary of the performance shares activity, with share amounts representing the target number of performance shares, was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested shares, January 1 | 144,424 |  |  | 139,940 |  |  | 145,277 |
Granted | 45,403 |  |  | 51,221 |  |  | 49,093 |
Vested | (45,612 | ) |  | (45,235 | ) |  | (54,430 | )
Forfeited | — |  |  | (1,502 | ) |  | — |
Nonvested shares, December 31 | 144,215 |  |  | 144,424 |  |  | 139,940 |
Certain performance shares vested, resulting in payouts (a combination of cash and common stock) as follows:
| 2015 |  | 2014 |  | 2013
| 2012 Grant |  | 2011 Grant |  | 2010 Grant
Performance shares vested | 45,612 |  |  | 45,235 |  |  | 54,430 |
Percentage of target number of performance shares | 167.5 | % |  | 147.5 | % |  | 197.5 | %
Aggregate payout value (in millions) |  | $5.1 |  |  |  | $3.4 |  |  |  | $4.8 |
Payout - cash (in millions) |  | $3.2 |  |  |  | $2.9 |  |  |  | $4.4 |
Payout - common stock shares issued | 10,975 |  |  | 4,810 |  |  | 4,177 |
Performance Units - Performance units must be paid out in cash. Each performance unit’s value is based on the average price of one share of Alliant Energy’s common stock on the grant date of the award. The actual payout for performance units is dependent upon actual performance and may range from zero to 200% of the target number of units. A summary of the performance unit activity, with amounts representing the target number of performance units, was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested units, January 1 | 63,665 |  |  | 65,912 |  |  | 64,969 |
Granted | 17,837 |  |  | 20,422 |  |  | 22,201 |
Vested | (22,845 | ) |  | (20,751 | ) |  | (19,760 | )
Forfeited | (451 | ) |  | (1,918 | ) |  | (1,498 | )
Nonvested units, December 31 | 58,206 |  |  | 63,665 |  |  | 65,912 |
Certain performance units vested, resulting in cash payouts as follows:
| 2015 |  | 2014 |  | 2013
| 2012 Grant |  | 2011 Grant |  | 2010 Grant
Performance units vested | 22,845 |  |  | 20,751 |  |  | 19,760 |
Percentage of target number of performance units | 167.5 | % |  | 147.5 | % |  | 197.5 | %
Payout value (in millions) |  | $1.6 |  |  |  | $1.2 |  |  |  | $1.3 |
Fair Value of Awards - Information related to fair values of nonvested performance shares and units at December 31, 2015, by year of grant, were as follows:
| Performance Shares |  | Performance Units
| 2015 Grant |  | 2014 Grant |  | 2013 Grant |  | 2015 Grant |  | 2014 Grant |  | 2013 Grant
Nonvested awards | 45,403 |  |  | 49,719 |  |  | 49,093 |  |  | 17,386 |  |  | 19,440 |  |  | 21,380 |
Alliant Energy common stock closing price on December 31, 2015 |  | $62.45 |  |  |  | $62.45 |  |  |  | $62.45 |  |  |  |  |  |  |
Alliant Energy common stock closing price on grant date |  |  |  |  |  |  |  | $65.09 |  |  |  | $53.77 |  |  |  | $47.58 |
Estimated payout percentage based on performance criteria | 80 | % |  | 125 | % |  | 165 | % |  | 80 | % |  | 125 | % |  | 165 | %
Fair values of each nonvested award |  | $49.96 |  |  |  | $78.06 |  |  |  | $103.04 |  |  |  | $52.07 |  |  |  | $67.21 |  |  |  | $78.51 |
At December 31, 2015, fair values of nonvested performance shares and units were calculated based on Alliant Energy’s stock price and anticipated total shareowner returns of Alliant Energy and its investor-owned utility peer group over the performance period. The portion of the fair values based on anticipated total shareowner returns was estimated using a model that incorporates the probability of meeting performance targets based on historical returns relative to the peer group. Performance-Contingent Restricted Stock - Vesting of performance-contingent restricted stock grants are based on the achievement of certain performance targets (currently specified growth of consolidated income from continuing operations). If performance targets are not met within the performance period, which currently ranges from two to four years, these restricted stock grants are forfeited. Payouts of nonvested performance-contingent restricted stock are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of performance-contingent restricted stock to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested performance-contingent restricted stock is forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. The fair value of performance-contingent restricted stock is based on the closing market price on the grant date. A summary of the performance-contingent restricted stock activity was as follows:
| 2015 |  | 2014 |  | 2013
| Shares |  | Weighted Average Fair Value |  | Shares |  | Weighted Average Fair Value |  | Shares |  | Weighted Average Fair Value
Nonvested shares, January 1 | 98,812 |  |  |  | $50.69 |  |  | 158,922 |  |  |  | $42.71 |  |  | 211,651 |  |  |  | $32.42 |
Granted | 45,403 |  |  | 65.09 |  |  | 51,221 |  |  | 53.77 |  |  | 49,093 |  |  | 47.58 |
Vested (a) | (49,093 | ) |  | 47.58 |  |  | (90,847 | ) |  | 40.91 |  |  | — |  |  | — |
Forfeited (b) | — |  |  | — |  |  | (20,484 | ) |  | 39.85 |  |  | (101,822 | ) |  | 23.67 |
Nonvested shares, December 31 | 95,122 |  |  | 59.17 |  |  | 98,812 |  |  | 50.69 |  |  | 158,922 |  |  | 42.71 |
(a) | In 2015, 49,093 performance-contingent restricted shares granted in 2013 vested because the specified performance criteria for such shares were met. In 2014, 45,612 and 45,235 performance-contingent restricted shares granted in 2012 and 2011, respectively, vested because the specified performance criteria for such shares were met.
(b) | In 2013, 101,822 performance-contingent restricted shares granted in 2009 were forfeited because the specified performance criteria for such shares were not met. The forfeitures during 2014 were primarily caused by retirements and terminations of participants.
Performance-Contingent Cash Awards - Performance-contingent cash award payouts to key employees are based on the achievement of certain performance targets (currently specified growth of consolidated income from continuing operations). If performance targets are not met within the performance period, which currently ranges from two to four years, there are no payouts for these awards. Payouts of nonvested awards are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of these awards to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested awards are forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. Each performance-contingent cash award’s value is based on the price of one share of Alliant Energy’s common stock at the end of the performance period. Alliant Energy accounts for performance-contingent cash awards as liability awards because payouts will be made in the form of cash. A summary of the performance-contingent cash awards activity was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested awards, January 1 | 78,930 |  |  | 96,977 |  |  | 59,639 |
Granted | 41,105 |  |  | 42,446 |  |  | 39,530 |
Vested (a) | (37,332 | ) |  | (55,517 | ) |  | — |
Forfeited | (827 | ) |  | (4,976 | ) |  | (2,192 | )
Nonvested awards, December 31 | 81,876 |  |  | 78,930 |  |  | 96,977 |
(a) | In 2015, 37,332 performance-contingent cash awards granted in 2013 vested, resulting in cash payouts valued at $2.4 million. In 2014, 34,766 and 20,751 performance-contingent cash awards granted in 2012 and 2011 vested, resulting in cash payouts valued at $1.9 million and $1.1 million, respectively.
(c) Deferred Compensation Plan - Alliant Energy maintains a DCP under which key employees may defer up to 100% of base salary and performance-based compensation and directors may elect to defer all or part of their retainer and committee fees. Key employees who have made the maximum allowed contribution to the Alliant Energy 401(k) Savings Plan may receive an additional credit to the DCP. Key employees and directors may elect to have their deferrals credited to a company stock account, an interest account or equity accounts based on certain benchmark funds. Company Stock Accounts - The DCP does not permit diversification of deferrals credited to the company stock account and all distributions from participants’ company stock accounts are made in the form of shares of Alliant Energy common stock. The deferred compensation obligations for participants’ company stock accounts are recorded in “Additional paid-in capital” and the shares of Alliant Energy common stock held in a rabbi trust to satisfy this obligation are recorded in “Shares in deferred compensation trust” on Alliant Energy’s balance sheets. At December 31, the carrying value of the deferred compensation obligation for the company stock accounts and the shares in the deferred compensation trust based on the historical value of the shares of Alliant Energy common stock contributed to the rabbi trust, and the fair market value of the shares held in the rabbi trust were as follows (in millions):
| 2015 |  | 2014
Carrying value |  | $8.5 |  |  |  | $8.9 |
Fair market value | 13.4 |  |  | 15.9 |
Interest and Equity Accounts - Distributions from participants’ interest and equity accounts are in the form of cash payments. The deferred compensation obligations for participants’ interest and equity accounts are recorded in “Pension and other benefit obligations” on Alliant Energy’s and IPL’s balance sheets. At December 31, the carrying value of deferred compensation obligations for participants’ interest and equity accounts, which approximates fair market value, was as follows (in millions):
| Alliant Energy |  | IPL
| 2015 |  | 2014 |  | 2015 |  | 2014
Carrying value | $18.3 |  | $17.8 |  | $5.0 |  | $5.2
WPL [Member] |
Benefit Plans | BENEFIT PLANS (a) Pension and Other Postretirement Benefits Plans - Retirement benefits are provided to substantially all employees through various qualified and non-qualified non-contributory defined benefit pension plans, and/or through defined contribution plans (including 401(k) savings plans). Qualified and non-qualified non-contributory defined benefit pension plans are currently closed to new hires. Benefits of the non-contributory defined benefit pension plans are based on the plan participant’s years of service, age and compensation. Benefits of the defined contribution plans are based on the plan participant’s years of service, age, compensation and contributions. Certain defined benefit postretirement health care and life benefits are provided to eligible retirees. In general, the retiree health care plans consist of fixed benefit subsidy structures and the retiree life insurance plans are non-contributory. IPL and WPL account for their participation in Alliant Energy and Corporate Services sponsored plans as multiple-employer plans. Assumptions - The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows:
| Defined Benefit Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.47% |  | 4.18% |  | 4.97% |  | 4.30% |  | 3.97% |  | 4.59%
Discount rate for net periodic cost | 4.18% |  | 4.97% |  | 4.11% |  | 3.97% |  | 4.59% |  | 3.82%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 6.20% |  | 7.40% |  | 7.40%
Rate of compensation increase | 3.65 | % | - | 4.50% |  | 3.50 | % | - | 4.50% |  | 3.50 | % | - | 4.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
| Qualified Defined Benefit Pension Plan |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.50% |  | 4.20% |  | 5.05% |  | 4.28% |  | 3.94% |  | 4.55%
Discount rate for net periodic cost | 4.20% |  | 5.05% |  | 4.20% |  | 3.94% |  | 4.55% |  | 3.76%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 6.60% |  | 7.60% |  | 7.50%
Rate of compensation increase | 3.65% |  | 3.50% |  | 3.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
| Qualified Defined Benefit Pension Plan |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Discount rate for benefit obligations | 4.51% |  | 4.20% |  | 5.05% |  | 4.28% |  | 3.96% |  | 4.56%
Discount rate for net periodic cost | 4.20% |  | 5.05% |  | 4.20% |  | 3.96% |  | 4.56% |  | 3.81%
Expected rate of return on plan assets | 7.60% |  | 7.60% |  | 7.60% |  | 4.60% |  | 7.30% |  | 7.20%
Rate of compensation increase | 3.65% |  | 3.50% |  | 3.50% |  | N/A |  | N/A |  | 3.50%
Medical cost trend on covered charges: |  |  |  |  |  |  |  |  |  |  |
Initial trend rate (end of year) | N/A |  | N/A |  | N/A |  | 7.25% |  | 6.75% |  | 7.00%
Ultimate trend rate | N/A |  | N/A |  | N/A |  | 5.00% |  | 5.00% |  | 5.00%
Expected rate of return on plan assets - The expected rate of return on plan assets is determined by analysis of projected asset class returns based on the target asset class allocations. A forward-looking building blocks approach is used, and historical returns, survey information and capital market information are reviewed to support the expected rate of return on plan assets assumption. Refer to “Investment Policy and Strategy for Plan Assets” below for additional information related to investment policy, and strategy and mix of assets for the pension and OPEB plans. Life Expectancy - The life expectancy assumption is used in determining the benefit obligation and net periodic benefit cost for defined benefit pension and OPEB plans. This assumption was updated as of December 31, 2014 and 2015 to utilize new mortality tables that were released in 2014 by the Society of Actuaries and updated in 2015, respectively. Net Periodic Benefit Costs (Credits) - The components of net periodic benefit costs (credits) for sponsored defined benefit pension and OPEB plans are included in the tables below (in millions). In IPL’s and WPL’s tables below, the defined benefit pension plans costs represent those respective costs for their bargaining unit employees covered under the qualified plans that they sponsor, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In IPL’s and WPL’s tables below, the OPEB plans costs (credits) represent respective costs (credits) for their employees, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Corporate Services sponsored OPEB plan.
Alliant Energy | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $15.9 |  |  |  | $13.1 |  |  |  | $15.7 |  |  |  | $5.5 |  |  |  | $5.2 |  |  |  | $6.3 |
Interest cost | 53.6 |  |  | 54.1 |  |  | 49.0 |  |  | 9.1 |  |  | 9.5 |  |  | 8.5 |
Expected return on plan assets (a) | (75.0 | ) |  | (74.9 | ) |  | (74.0 | ) |  | (8.4 | ) |  | (8.3 | ) |  | (8.1 | )
Amortization of prior service cost (credit) (b) | (0.2 | ) |  | — |  |  | 0.2 |  |  | (11.3 | ) |  | (11.9 | ) |  | (11.9 | )
Amortization of actuarial loss (c) | 35.4 |  |  | 19.5 |  |  | 36.2 |  |  | 4.8 |  |  | 2.4 |  |  | 4.9 |
Additional benefit costs (d) | 0.5 |  |  | — |  |  | 9.0 |  |  | — |  |  | — |  |  | — |
|  | $30.2 |  |  |  | $11.8 |  |  |  | $36.1 |  |  |  | ($0.3 | ) |  |  | ($3.1 | ) |  |  | ($0.3 | )
IPL | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $8.8 |  |  |  | $7.2 |  |  |  | $8.6 |  |  |  | $2.4 |  |  |  | $2.4 |  |  |  | $2.9 |
Interest cost | 25.0 |  |  | 25.1 |  |  | 22.9 |  |  | 3.8 |  |  | 3.9 |  |  | 3.6 |
Expected return on plan assets (a) | (35.8 | ) |  | (35.7 | ) |  | (35.2 | ) |  | (5.7 | ) |  | (5.8 | ) |  | (5.6 | )
Amortization of prior service cost (credit) (b) | (0.1 | ) |  | — |  |  | 0.1 |  |  | (6.1 | ) |  | (6.3 | ) |  | (6.3 | )
Amortization of actuarial loss (c) | 15.3 |  |  | 8.0 |  |  | 15.2 |  |  | 2.3 |  |  | 1.1 |  |  | 2.7 |
Additional benefit costs (d) | — |  |  | — |  |  | 2.6 |  |  | — |  |  | — |  |  | — |
|  | $13.2 |  |  |  | $4.6 |  |  |  | $14.2 |  |  |  | ($3.3 | ) |  |  | ($4.7 | ) |  |  | ($2.7 | )
WPL | Defined Benefit Pension Plans |  | OPEB Plans
2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Service cost |  | $5.8 |  |  |  | $4.9 |  |  |  | $5.9 |  |  |  | $2.1 |  |  |  | $2.0 |  |  |  | $2.5 |
Interest cost | 22.6 |  |  | 22.6 |  |  | 20.7 |  |  | 3.7 |  |  | 3.8 |  |  | 3.4 |
Expected return on plan assets (a) | (32.4 | ) |  | (32.4 | ) |  | (31.9 | ) |  | (1.5 | ) |  | (1.3 | ) |  | (1.3 | )
Amortization of prior service cost (credit) (b) | 0.2 |  |  | 0.3 |  |  | 0.3 |  |  | (3.5 | ) |  | (3.9 | ) |  | (3.9 | )
Amortization of actuarial loss (c) | 16.8 |  |  | 9.2 |  |  | 17.1 |  |  | 2.2 |  |  | 1.3 |  |  | 1.9 |
Additional benefit costs (d) | 0.5 |  |  | — |  |  | 0.6 |  |  | — |  |  | — |  |  | — |
|  | $13.5 |  |  |  | $4.6 |  |  |  | $12.7 |  |  |  | $3.0 |  |  |  | $1.9 |  |  |  | $2.6 |
(a) | The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets.
(b) | Unrecognized prior service costs (credits) for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan.
(c) | Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Cash Balance Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits.
(d) | In 2013, Alliant Energy filed a stipulation agreement with the Western Wisconsin Court related to a class-action lawsuit against the Cash Balance Plan. As a result, Alliant Energy recognized $9.0 million of additional benefits costs in 2013 related to the agreement. IPL recognized $5.5 million ($2.6 million directly assigned and $2.9 million allocated by Corporate Services) and WPL recognized $2.8 million ($0.6 million directly assigned and $2.2 million allocated by Corporate Services) of additional benefits costs in 2013 related to the agreement.
The estimated amortization from “Regulatory assets” and “Regulatory liabilities” on the balance sheets and AOCL on Alliant Energy’s balance sheet into net periodic benefit cost in 2016 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Defined Benefit |  |  |  | Defined Benefit |  |  |  | Defined Benefit |  |
| Pension Plans |  | OPEB Plans |  | Pension Plans |  | OPEB Plans |  | Pension Plans |  | OPEB Plans
Actuarial loss |  | $37.4 |  |  |  | $4.8 |  |  |  | $16.5 |  |  |  | $2.6 |  |  |  | $17.6 |  |  |  | $1.8 |
Prior service cost (credit) | (0.3 | ) |  | (4.1 | ) |  | (0.2 | ) |  | (2.6 | ) |  | 0.2 |  |  | (0.9 | )
|  | $37.1 |  |  |  | $0.7 |  |  |  | $16.3 |  |  |  | $— |  |  |  | $17.8 |  |  |  | $0.9 |
Net periodic benefit costs are primarily included in “Other operation and maintenance” in the income statements. Benefit Plan Assets and Obligations - A reconciliation of the funded status of Alliant Energy’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on Alliant Energy’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $1,301.5 |  |  |  | $1,113.4 |  |  |  | $231.1 |  |  |  | $208.7 |
Service cost | 15.9 |  |  | 13.1 |  |  | 5.5 |  |  | 5.2 |
Interest cost | 53.6 |  |  | 54.1 |  |  | 9.1 |  |  | 9.5 |
Plan participants’ contributions | — |  |  | — |  |  | 3.1 |  |  | 2.8 |
Plan amendments | — |  |  | — |  |  | (0.3 | ) |  | — |
Additional benefit costs | 0.5 |  |  | — |  |  | — |  |  | — |
Actuarial (gain) loss | (70.1 | ) |  | 195.8 |  |  | (9.4 | ) |  | 22.3 |
Gross benefits paid | (95.1 | ) |  | (74.9 | ) |  | (17.7 | ) |  | (17.4 | )
Net benefit obligation at December 31 | 1,206.3 |  |  | 1,301.5 |  |  | 221.4 |  |  | 231.1 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 1,018.1 |  |  | 1,022.9 |  |  | 121.6 |  |  | 124.9 |
Actual return on plan assets | (30.2 | ) |  | 66.4 |  |  | (4.9 | ) |  | 5.6 |
Employer contributions | 2.2 |  |  | 3.7 |  |  | 4.8 |  |  | 5.7 |
Plan participants’ contributions | — |  |  | — |  |  | 3.1 |  |  | 2.8 |
Gross benefits paid | (95.1 | ) |  | (74.9 | ) |  | (17.7 | ) |  | (17.4 | )
Fair value of plan assets at December 31 | 895.0 |  |  | 1,018.1 |  |  | 106.9 |  |  | 121.6 |
Under funded status at December 31 |  | ($311.3 | ) |  |  | ($283.4 | ) |  |  | ($114.5 | ) |  |  | ($109.5 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $3.0 |  |  |  | $6.1 |
Other current liabilities | (2.6 | ) |  | (2.5 | ) |  | (6.2 | ) |  | (5.6 | )
Pension and other benefit obligations | (308.7 | ) |  | (280.9 | ) |  | (111.3 | ) |  | (110.0 | )
Net amounts recognized at December 31 |  | ($311.3 | ) |  |  | ($283.4 | ) |  |  | ($114.5 | ) |  |  | ($109.5 | )
Amounts recognized in Regulatory Assets and AOCL consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $533.1 |  |  |  | $533.4 |  |  |  | $59.8 |  |  |  | $60.7 |
Prior service credit | (7.2 | ) |  | (7.4 | ) |  | (5.6 | ) |  | (16.7 | )
|  | $525.9 |  |  |  | $526.0 |  |  |  | $54.2 |  |  |  | $44.0 |
(a) | Refer to Note 2 and Alliant Energy’s common equity statements for amounts recognized in “Regulatory assets” and “AOCL,” respectively, on Alliant Energy’s balance sheets.
In IPL’s and WPL’s tables below, the defined benefit pension plans amounts represent those respective amounts for their bargaining unit employees covered under the qualified plans that they sponsor, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans. In IPL’s and WPL’s tables below, the OPEB plans amounts represent respective amounts for their employees, as well as amounts directly assigned to them related to their current and former non-bargaining employees who are participants in the Corporate Services sponsored OPEB plan. A reconciliation of the funded status of IPL’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on IPL’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $603.1 |  |  |  | $514.0 |  |  |  | $96.4 |  |  |  | $87.8 |
Service cost | 8.8 |  |  | 7.2 |  |  | 2.4 |  |  | 2.4 |
Interest cost | 25.0 |  |  | 25.1 |  |  | 3.8 |  |  | 3.9 |
Plan participants’ contributions | — |  |  | — |  |  | 1.0 |  |  | 0.9 |
Plan amendments | — |  |  | — |  |  | (0.1 | ) |  | — |
Actuarial (gain) loss | (32.3 | ) |  | 91.4 |  |  | (4.6 | ) |  | 8.6 |
Gross benefits paid | (48.5 | ) |  | (34.6 | ) |  | (7.6 | ) |  | (7.2 | )
Net benefit obligation at December 31 | 556.1 |  |  | 603.1 |  |  | 91.3 |  |  | 96.4 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 484.7 |  |  | 485.9 |  |  | 78.7 |  |  | 81.2 |
Actual return on plan assets | (14.3 | ) |  | 32.1 |  |  | (3.1 | ) |  | 3.6 |
Employer contributions | 0.8 |  |  | 1.3 |  |  | 0.2 |  |  | 0.2 |
Plan participants’ contributions | — |  |  | — |  |  | 1.0 |  |  | 0.9 |
Gross benefits paid | (48.5 | ) |  | (34.6 | ) |  | (7.6 | ) |  | (7.2 | )
Fair value of plan assets at December 31 | 422.7 |  |  | 484.7 |  |  | 69.2 |  |  | 78.7 |
Under funded status at December 31 |  | ($133.4 | ) |  |  | ($118.4 | ) |  |  | ($22.1 | ) |  |  | ($17.7 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $— |  |  |  | $1.2 |
Other current liabilities | (0.8 | ) |  | (0.8 | ) |  | — |  |  | — |
Pension and other benefit obligations | (132.6 | ) |  | (117.6 | ) |  | (22.1 | ) |  | (18.9 | )
Net amounts recognized at December 31 |  | ($133.4 | ) |  |  | ($118.4 | ) |  |  | ($22.1 | ) |  |  | ($17.7 | )
Amounts recognized in Regulatory Assets consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $235.5 |  |  |  | $233.1 |  |  |  | $29.8 |  |  |  | $27.9 |
Prior service credit | (2.5 | ) |  | (2.6 | ) |  | (2.7 | ) |  | (8.7 | )
|  | $233.0 |  |  |  | $230.5 |  |  |  | $27.1 |  |  |  | $19.2 |
(a) | Refer to Note 2 for amounts recognized in “Regulatory assets” on IPL’s balance sheets.
A reconciliation of the funded status of WPL’s qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on WPL’s balance sheets at December 31 was as follows (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Change in benefit obligation: |  |  |  |  |  |  |
Net benefit obligation at January 1 |  | $547.6 |  |  |  | $460.8 |  |  |  | $94.0 |  |  |  | $85.6 |
Service cost | 5.8 |  |  | 4.9 |  |  | 2.1 |  |  | 2.0 |
Interest cost | 22.6 |  |  | 22.6 |  |  | 3.7 |  |  | 3.8 |
Plan participants’ contributions | — |  |  | — |  |  | 1.6 |  |  | 1.3 |
Plan amendments | — |  |  | — |  |  | (0.2 | ) |  | — |
Additional benefit costs | 0.5 |  |  | — |  |  | — |  |  | — |
Actuarial (gain) loss | (30.0 | ) |  | 86.7 |  |  | (3.5 | ) |  | 9.2 |
Gross benefits paid | (40.6 | ) |  | (27.4 | ) |  | (8.0 | ) |  | (7.9 | )
Net benefit obligation at December 31 | 505.9 |  |  | 547.6 |  |  | 89.7 |  |  | 94.0 |
Change in plan assets: |  |  |  |  |  |  |
Fair value of plan assets at January 1 | 440.3 |  |  | 438.8 |  |  | 21.8 |  |  | 21.7 |
Actual return on plan assets | (13.0 | ) |  | 28.6 |  |  | (1.1 | ) |  | 1.2 |
Employer contributions | 0.1 |  |  | 0.3 |  |  | 4.4 |  |  | 5.5 |
Plan participants’ contributions | — |  |  | — |  |  | 1.6 |  |  | 1.3 |
Gross benefits paid | (40.6 | ) |  | (27.4 | ) |  | (8.0 | ) |  | (7.9 | )
Fair value of plan assets at December 31 | 386.8 |  |  | 440.3 |  |  | 18.7 |  |  | 21.8 |
Under funded status at December 31 |  | ($119.1 | ) |  |  | ($107.3 | ) |  |  | ($71.0 | ) |  |  | ($72.2 | )
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Amounts recognized on the balance sheets consist of: |  |  |  |  |  |  |
Non-current assets |  | $— |  |  |  | $— |  |  |  | $3.0 |  |  |  | $4.9 |
Other current liabilities | (0.1 | ) |  | (0.1 | ) |  | (6.0 | ) |  | (5.5 | )
Pension and other benefit obligations | (119.0 | ) |  | (107.2 | ) |  | (68.0 | ) |  | (71.6 | )
Net amounts recognized at December 31 |  | ($119.1 | ) |  |  | ($107.3 | ) |  |  | ($71.0 | ) |  |  | ($72.2 | )
Amounts recognized in Regulatory Assets consist of (a): |  |  |  |  |  |  |
Net actuarial loss |  | $232.1 |  |  |  | $233.5 |  |  |  | $23.3 |  |  |  | $26.3 |
Prior service credit | (1.2 | ) |  | (1.0 | ) |  | (2.4 | ) |  | (5.6 | )
|  | $230.9 |  |  |  | $232.5 |  |  |  | $20.9 |  |  |  | $20.7 |
(a) | Refer to Note 2 for amounts recognized in “Regulatory assets” on WPL’s balance sheets.
Included in the following tables are accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date (in millions):
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
Alliant Energy | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $1,166.0 |  |  |  | $1,255.0 |  |  |  | $221.4 |  |  |  | $231.1 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 1,166.0 |  |  | 1,255.0 |  |  | 221.4 |  |  | 231.1 |
Fair value of plan assets | 895.0 |  |  | 1,018.1 |  |  | 106.9 |  |  | 121.6 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 1,206.3 |  |  | 1,301.5 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 895.0 |  |  | 1,018.1 |  |  | N/A |  |  | N/A |
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
IPL | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $531.0 |  |  |  | $575.5 |  |  |  | $91.3 |  |  |  | $96.4 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 531.0 |  |  | 575.5 |  |  | 91.3 |  |  | 96.4 |
Fair value of plan assets | 422.7 |  |  | 484.7 |  |  | 69.2 |  |  | 78.7 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 556.1 |  |  | 603.1 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 422.7 |  |  | 484.7 |  |  | N/A |  |  | N/A |
| Defined Benefit |  |
| Pension Plans |  | OPEB Plans
WPL | 2015 |  | 2014 |  | 2015 |  | 2014
Accumulated benefit obligations |  | $493.8 |  |  |  | $532.5 |  |  |  | $89.7 |  |  |  | $94.0 |
Plans with accumulated benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Accumulated benefit obligations | 493.8 |  |  | 532.5 |  |  | 89.7 |  |  | 94.0 |
Fair value of plan assets | 386.8 |  |  | 440.3 |  |  | 18.7 |  |  | 21.8 |
Plans with projected benefit obligations in excess of plan assets: |  |  |  |  |  |  |
Projected benefit obligations | 505.9 |  |  | 547.6 |  |  | N/A |  |  | N/A |
Fair value of plan assets | 386.8 |  |  | 440.3 |  |  | N/A |  |  | N/A |
In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions):
| IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014
Regulatory assets |  | $38.0 |  |  |  | $38.2 |  |  |  | $29.5 |  |  |  | $28.0 |
Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2016 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Defined benefit pension plans (a) |  | $2.6 |  |  |  | $0.8 |  |  |  | $0.1 |
OPEB plans | 5.8 |  |  | — |  |  | 5.5 |
(a) | Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans.
Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions):
Alliant Energy | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $69.5 |  |  |  | $74.3 |  |  |  | $72.8 |  |  |  | $74.3 |  |  |  | $78.7 |  |  |  | $401.4 |
OPEB | 17.8 |  |  | 18.1 |  |  | 18.2 |  |  | 18.3 |  |  | 18.2 |  |  | 86.9 |
|  | $87.3 |  |  |  | $92.4 |  |  |  | $91.0 |  |  |  | $92.6 |  |  |  | $96.9 |  |  |  | $488.3 |
IPL | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $32.8 |  |  |  | $34.1 |  |  |  | $34.8 |  |  |  | $34.6 |  |  |  | $37.8 |  |  |  | $190.8 |
OPEB | 7.6 |  |  | 7.6 |  |  | 7.6 |  |  | 7.5 |  |  | 7.6 |  |  | 36.0 |
|  | $40.4 |  |  |  | $41.7 |  |  |  | $42.4 |  |  |  | $42.1 |  |  |  | $45.4 |  |  |  | $226.8 |
WPL | 2016 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2021 - 2025
Defined benefit pension benefits |  | $29.1 |  |  |  | $29.8 |  |  |  | $30.7 |  |  |  | $31.1 |  |  |  | $32.2 |  |  |  | $163.7 |
OPEB | 7.5 |  |  | 7.8 |  |  | 7.8 |  |  | 7.8 |  |  | 7.6 |  |  | 34.7 |
|  | $36.6 |  |  |  | $37.6 |  |  |  | $38.5 |  |  |  | $38.9 |  |  |  | $39.8 |  |  |  | $198.4 |
Investment Policy and Strategy for Plan Assets - Investment policies and strategies employed with respect to assets of defined benefit pension and OPEB plans are to combine both preservation of principal and prudent and reasonable risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term. It is recognized that risk and volatility are present with all types of investments. However, risk is mitigated at the total fund level through diversification by asset class including U.S. and international equity and fixed income exposure, global asset and risk parity strategies, the number of individual investments, and sector and industry limits. Global asset and risk parity strategies include investments in global equity, global debt, commodities and currencies. Defined Benefit Pension Plan Assets - For assets of defined benefit pension plans, the mix among asset classes is controlled by asset allocation targets. Historical performance results and future expectations suggest that equity securities will provide higher total investment returns than debt securities over a long-term investment horizon. Consistent with the goals of meeting obligations to plan participants and minimizing benefit costs over the long-term, the defined benefit pension plans have a long-term investment posture more heavily weighted towards equity holdings. The asset allocation is monitored regularly and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. An overlay management service is also used to help maintain target allocations and meet liquidity needs. The overlay manager is authorized to use derivative financial instruments to facilitate this service. For separately managed accounts, prohibited investment vehicles include, but may not be limited to, direct ownership of real estate, margin trading, oil and gas limited partnerships and securities of the managers’ firms or affiliate firms. At December 31, 2015, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows:
| Target Range |  | Actual
| Allocation |  | Allocation
Cash and equivalents | 0 | % | - | 5% |  | 2%
Equity securities: |  |  |  |  |
U.S. large cap core | 8 | % | - | 18% |  | 11%
U.S. large cap value | 2.5 | % | - | 12.5% |  | 7%
U.S. large cap growth | 2.5 | % | - | 12.5% |  | 7%
U.S. small cap value | 0 | % | - | 4% |  | 1%
U.S. small cap growth | 0 | % | - | 4% |  | 2%
International - developed markets | 7 | % | - | 19% |  | 12%
International - emerging markets | 0 | % | - | 10% |  | 5%
Global asset allocation securities | 5 | % | - | 15% |  | 11%
Risk parity allocation securities | 5 | % | - | 15% |  | 10%
Fixed income securities | 20 | % | - | 40% |  | 32%
Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts. The investment policy and strategy of the 401(h) assets, except for the WPL 401(h) assets, mirrors those of the defined benefit pension plans, which are discussed above. For VEBA trusts with assets greater than $5 million and the WPL 401(h) assets, the mix among asset classes is controlled by allocation targets. The asset allocation is monitored regularly and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. Mutual funds are used to achieve the desired diversification. At December 31, 2015, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows:
| Target Range |  | Actual
| Allocation |  | Allocation
Cash and equivalents | 0 | % | - | 15% |  | 3%
Equity securities: |  |  |  |  |
Domestic | 0 | % | - | 45% |  | 21%
International | 0 | % | - | 21% |  | 13%
Global asset allocation securities | 5 | % | - | 40% |  | 16%
Fixed income securities | 10 | % | - | 70% |  | 47%
Fair Value Measurements - The following tables report a framework for measuring fair value. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value. The three levels of the fair value hierarchy and examples of each are as follows: Level 1 - Pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. Investments in securities held in registered investment companies and directly held equity securities are valued at the closing price reported in the active market in which the securities are traded. Level 2 - Pricing inputs are quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability and inputs that are derived principally from or corroborated by observable market data by correlation or other means. Investments in common/collective trusts are valued at the net asset value of shares held by the plans, which is based on the fair market value of the underlying investments in the common/collective trusts. Investments in corporate bonds are valued at the closing price reported in the active market for similar assets in which the individual securities are traded or based on yields currently available on comparable securities of issuers with similar credit ratings. Level 3 - Pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability. The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while Alliant Energy, IPL and WPL believe their valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date. At December 31, the fair values of Alliant Energy’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $23.1 |  |  |  | $— |  |  |  | $23.1 |  |  |  | $— |  |  |  | $49.3 |  |  |  | $— |  |  |  | $49.3 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 100.4 |  |  | 100.4 |  |  | — |  |  | — |  |  | 137.2 |  |  | 137.2 |  |  | — |  |  | — |
U.S. large cap value | 59.9 |  |  | — |  |  | 59.9 |  |  | — |  |  | 72.2 |  |  | — |  |  | 72.2 |  |  | — |
U.S. large cap growth | 60.5 |  |  | — |  |  | 60.5 |  |  | — |  |  | 73.2 |  |  | — |  |  | 73.2 |  |  | — |
U.S. small cap value | 14.2 |  |  | — |  |  | 14.2 |  |  | — |  |  | 15.2 |  |  | — |  |  | 15.2 |  |  | — |
U.S. small cap growth | 16.0 |  |  | 16.0 |  |  | — |  |  | — |  |  | 15.9 |  |  | 15.9 |  |  | — |  |  | — |
International - developed markets | 104.4 |  |  | 52.7 |  |  | 51.7 |  |  | — |  |  | 102.9 |  |  | 52.1 |  |  | 50.8 |  |  | — |
International - emerging markets | 41.2 |  |  | 41.2 |  |  | — |  |  | — |  |  | 47.2 |  |  | 47.2 |  |  | — |  |  | — |
Global asset allocation securities | 96.3 |  |  | 52.9 |  |  | 43.4 |  |  | — |  |  | 99.9 |  |  | 57.2 |  |  | 42.7 |  |  | — |
Risk parity allocation securities | 94.0 |  |  | — |  |  | 94.0 |  |  | — |  |  | 102.5 |  |  | — |  |  | 102.5 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.1 |  |  | — |
Fixed income funds | 284.8 |  |  | — |  |  | 284.8 |  |  | — |  |  | 302.7 |  |  | 0.2 |  |  | 302.5 |  |  | — |
| 894.8 |  |  |  | $263.2 |  |  |  | $631.6 |  |  |  | $— |  |  | 1,018.3 |  |  |  | $309.8 |  |  |  | $708.5 |  |  |  | $— |
Accrued investment income | 0.2 |  |  |  |  |  |  |  |  | 0.1 |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.3 | ) |  |  |  |  |  |
Total pension plan assets |  | $895.0 |  |  |  |  |  |  |  |  |  | $1,018.1 |  |  |  |  |  |  |
At December 31, the fair values of IPL’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $10.9 |  |  |  | $— |  |  |  | $10.9 |  |  |  | $— |  |  |  | $23.5 |  |  |  | $— |  |  |  | $23.5 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 47.4 |  |  | 47.4 |  |  | — |  |  | — |  |  | 65.3 |  |  | 65.3 |  |  | — |  |  | — |
U.S. large cap value | 28.3 |  |  | — |  |  | 28.3 |  |  | — |  |  | 34.4 |  |  | — |  |  | 34.4 |  |  | — |
U.S. large cap growth | 28.6 |  |  | — |  |  | 28.6 |  |  | — |  |  | 34.9 |  |  | — |  |  | 34.9 |  |  | — |
U.S. small cap value | 6.7 |  |  | — |  |  | 6.7 |  |  | — |  |  | 7.2 |  |  | — |  |  | 7.2 |  |  | — |
U.S. small cap growth | 7.5 |  |  | 7.5 |  |  | — |  |  | — |  |  | 7.6 |  |  | 7.6 |  |  | — |  |  | — |
International - developed markets | 49.3 |  |  | 24.9 |  |  | 24.4 |  |  | — |  |  | 49.0 |  |  | 24.8 |  |  | 24.2 |  |  | — |
International - emerging markets | 19.5 |  |  | 19.5 |  |  | — |  |  | — |  |  | 22.5 |  |  | 22.5 |  |  | — |  |  | — |
Global asset allocation securities | 45.5 |  |  | 25.0 |  |  | 20.5 |  |  | — |  |  | 47.5 |  |  | 27.2 |  |  | 20.3 |  |  | — |
Risk parity allocation securities | 44.4 |  |  | — |  |  | 44.4 |  |  | — |  |  | 48.8 |  |  | — |  |  | 48.8 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 134.5 |  |  | — |  |  | 134.5 |  |  | — |  |  | 144.1 |  |  | 0.1 |  |  | 144.0 |  |  | — |
| 422.6 |  |  |  | $124.3 |  |  |  | $298.3 |  |  |  | $— |  |  | 484.8 |  |  |  | $147.5 |  |  |  | $337.3 |  |  |  | $— |
Accrued investment income | 0.1 |  |  |  |  |  |  |  |  | 0.1 |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.2 | ) |  |  |  |  |  |
Total pension plan assets |  | $422.7 |  |  |  |  |  |  |  |  |  | $484.7 |  |  |  |  |  |  |
At December 31, the fair values of WPL’s qualified and non-qualified defined benefit pension plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $10.0 |  |  |  | $— |  |  |  | $10.0 |  |  |  | $— |  |  |  | $21.3 |  |  |  | $— |  |  |  | $21.3 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. large cap core | 43.4 |  |  | 43.4 |  |  | — |  |  | — |  |  | 59.3 |  |  | 59.3 |  |  | — |  |  | — |
U.S. large cap value | 25.9 |  |  | — |  |  | 25.9 |  |  | — |  |  | 31.3 |  |  | — |  |  | 31.3 |  |  | — |
U.S. large cap growth | 26.2 |  |  | — |  |  | 26.2 |  |  | — |  |  | 31.7 |  |  | — |  |  | 31.7 |  |  | — |
U.S. small cap value | 6.1 |  |  | — |  |  | 6.1 |  |  | — |  |  | 6.6 |  |  | — |  |  | 6.6 |  |  | — |
U.S. small cap growth | 6.9 |  |  | 6.9 |  |  | — |  |  | — |  |  | 6.9 |  |  | 6.9 |  |  | — |  |  | — |
International - developed markets | 45.1 |  |  | 22.8 |  |  | 22.3 |  |  | — |  |  | 44.5 |  |  | 22.5 |  |  | 22.0 |  |  | — |
International - emerging markets | 17.8 |  |  | 17.8 |  |  | — |  |  | — |  |  | 20.4 |  |  | 20.4 |  |  | — |  |  | — |
Global asset allocation securities | 41.6 |  |  | 22.8 |  |  | 18.8 |  |  | — |  |  | 43.2 |  |  | 24.8 |  |  | 18.4 |  |  | — |
Risk parity allocation securities | 40.6 |  |  | — |  |  | 40.6 |  |  | — |  |  | 44.3 |  |  | — |  |  | 44.3 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 123.1 |  |  | — |  |  | 123.1 |  |  | — |  |  | 130.9 |  |  | 0.1 |  |  | 130.8 |  |  | — |
| 386.7 |  |  |  | $113.7 |  |  |  | $273.0 |  |  |  | $— |  |  | 440.4 |  |  |  | $134.0 |  |  |  | $306.4 |  |  |  | $— |
Accrued investment income | 0.1 |  |  |  |  |  |  |  |  | — |  |  |  |  |  |  |
Due to brokers, net (pending trades with brokers) | — |  |  |  |  |  |  |  |  | (0.1 | ) |  |  |  |  |  |
Total pension plan assets |  | $386.8 |  |  |  |  |  |  |  |  |  | $440.3 |  |  |  |  |  |  |
At December 31, the fair values of Alliant Energy’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $3.6 |  |  |  | $— |  |  |  | $3.6 |  |  |  | $— |  |  |  | $3.7 |  |  |  | $— |  |  |  | $3.7 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | 21.1 |  |  | 21.1 |  |  | — |  |  | — |  |  | 35.8 |  |  | 35.8 |  |  | — |  |  | — |
U.S. large cap core | 0.9 |  |  | 0.9 |  |  | — |  |  | — |  |  | 2.9 |  |  | 2.9 |  |  | — |  |  | — |
U.S. large cap value | 0.5 |  |  | — |  |  | 0.5 |  |  | — |  |  | 1.5 |  |  | — |  |  | 1.5 |  |  | — |
U.S. large cap growth | 0.5 |  |  | — |  |  | 0.5 |  |  | — |  |  | 1.6 |  |  | — |  |  | 1.6 |  |  | — |
U.S. small cap value | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. small cap growth | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.4 |  |  | 0.4 |  |  | — |  |  | — |
International - blend | 12.5 |  |  | 12.5 |  |  | — |  |  | — |  |  | 14.2 |  |  | 14.2 |  |  | — |  |  | — |
International - developed markets | 1.0 |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | 2.2 |  |  | 1.1 |  |  | 1.1 |  |  | — |
International - emerging markets | 0.4 |  |  | 0.4 |  |  | — |  |  | — |  |  | 1.0 |  |  | 1.0 |  |  | — |  |  | — |
Global asset allocation securities | 16.4 |  |  | 16.0 |  |  | 0.4 |  |  | — |  |  | 30.3 |  |  | 29.4 |  |  | 0.9 |  |  | — |
Risk parity allocation securities | 0.9 |  |  | — |  |  | 0.9 |  |  | — |  |  | 2.2 |  |  | — |  |  | 2.2 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 48.9 |  |  | 46.3 |  |  | 2.6 |  |  | — |  |  | 25.5 |  |  | 19.0 |  |  | 6.5 |  |  | — |
Total OPEB plan assets |  | $106.9 |  |  |  | $97.8 |  |  |  | $9.1 |  |  |  | $— |  |  |  | $121.6 |  |  |  | $103.8 |  |  |  | $17.8 |  |  |  | $— |
At December 31, the fair values of IPL’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $0.9 |  |  |  | $— |  |  |  | $0.9 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | 16.6 |  |  | 16.6 |  |  | — |  |  | — |  |  | 27.2 |  |  | 27.2 |  |  | — |  |  | — |
U.S. large cap core | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | — |
U.S. large cap value | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. large cap growth | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.3 |  |  | — |  |  | 0.3 |  |  | — |
U.S. small cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.1 |  |  | — |
U.S. small cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.1 |  |  | 0.1 |  |  | — |  |  | — |
International - blend | 10.7 |  |  | 10.7 |  |  | — |  |  | — |  |  | 10.7 |  |  | 10.7 |  |  | — |  |  | — |
International - developed markets | 0.1 |  |  | 0.1 |  |  | — |  |  | — |  |  | 0.4 |  |  | 0.2 |  |  | 0.2 |  |  | — |
International - emerging markets | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | 0.2 |  |  | — |  |  | — |
Global asset allocation securities | 6.9 |  |  | 6.9 |  |  | — |  |  | — |  |  | 21.6 |  |  | 21.5 |  |  | 0.1 |  |  | — |
Risk parity allocation securities | 0.1 |  |  | — |  |  | 0.1 |  |  | — |  |  | 0.4 |  |  | — |  |  | 0.4 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 33.6 |  |  | 33.3 |  |  | 0.3 |  |  | — |  |  | 15.5 |  |  | 14.3 |  |  | 1.2 |  |  | — |
Total OPEB plan assets |  | $69.2 |  |  |  | $67.7 |  |  |  | $1.5 |  |  |  | $— |  |  |  | $78.7 |  |  |  | $74.7 |  |  |  | $4.0 |  |  |  | $— |
At December 31, the fair values of WPL’s OPEB plan assets by asset category and fair value hierarchy level were as follows (in millions):
| 2015 |  | 2014
| Fair |  | Level |  | Level |  | Level |  | Fair |  | Level |  | Level |  | Level
| Value |  | 1 |  | 2 |  | 3 |  | Value |  | 1 |  | 2 |  | 3
Cash and equivalents |  | $2.3 |  |  |  | $— |  |  |  | $2.3 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |  |  |  | $1.4 |  |  |  | $— |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. blend | — |  |  | — |  |  | — |  |  | — |  |  | 3.6 |  |  | 3.6 |  |  | — |  |  | — |
U.S. large cap core | — |  |  | — |  |  | — |  |  | — |  |  | 1.6 |  |  | 1.6 |  |  | — |  |  | — |
U.S. large cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.8 |  |  | — |  |  | 0.8 |  |  | — |
U.S. large cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.8 |  |  | — |  |  | 0.8 |  |  | — |
U.S. small cap value | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | — |  |  | 0.2 |  |  | — |
U.S. small cap growth | — |  |  | — |  |  | — |  |  | — |  |  | 0.2 |  |  | 0.2 |  |  | — |  |  | — |
International - blend | — |  |  | — |  |  | — |  |  | — |  |  | 1.4 |  |  | 1.4 |  |  | — |  |  | — |
International - developed markets | — |  |  | — |  |  | — |  |  | — |  |  | 1.2 |  |  | 0.6 |  |  | 0.6 |  |  | — |
International - emerging markets | — |  |  | — |  |  | — |  |  | — |  |  | 0.5 |  |  | 0.5 |  |  | — |  |  | — |
Global asset allocation securities | 5.4 |  |  | 5.4 |  |  | — |  |  | — |  |  | 3.8 |  |  | 3.3 |  |  | 0.5 |  |  | — |
Risk parity allocation securities | — |  |  | — |  |  | — |  |  | — |  |  | 1.1 |  |  | — |  |  | 1.1 |  |  | — |
Fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed income funds | 11.0 |  |  | 11.0 |  |  | — |  |  | — |  |  | 5.2 |  |  | 1.8 |  |  | 3.4 |  |  | — |
Total OPEB plan assets |  | $18.7 |  |  |  | $16.4 |  |  |  | $2.3 |  |  |  | $— |  |  |  | $21.8 |  |  |  | $13.0 |  |  |  | $8.8 |  |  |  | $— |
For the various defined benefit pension and OPEB plans, Alliant Energy common stock represented less than 1% of assets directly held in the plans at December 31, 2015 and 2014. 401(k) Savings Plans - A significant number of employees participate in defined contribution retirement plans (401(k) savings plans). Alliant Energy common stock represented 11.6% and 12.6% of total assets held in 401(k) savings plans at December 31, 2015 and 2014, respectively. Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  |  | 2014 |  |  | 2013 |  |  | 2015 |  | 2014 |  | 2013
401(k) costs |  | $24.9 |  |  |  | $22.5 |  |  |  | $19.2 |  |  |  | $12.7 |  |  |  | $11.1 |  |  |  | $9.9 |  |  |  | $11.2 |  |  |  | $10.5 |  |  |  | $8.5 |
Voluntary Employee Separation Charges - In 2015, Alliant Energy offered certain employees a voluntary separation package. Approximately 2% of total Alliant Energy employees accepted this package, which resulted in Alliant Energy, IPL and WPL recording charges of $8 million, $5 million and $3 million, respectively, in 2015. (b) Equity-based Compensation Plans - In 2015, Alliant Energy’s shareowners approved the Amended and Restated OIP, which permits the grant of shares of Alliant Energy common stock, restricted stock, restricted stock units, performance shares, performance units, and other stock-based or cash-based awards to key employees. At December 31, 2015, performance shares and restricted stock were outstanding and 3.8 million shares of Alliant Energy’s common stock remained available for grants under the Amended and Restated OIP. Alliant Energy satisfies share payouts related to equity awards under the Amended and Restated OIP through the issuance of new shares of its common stock. Alliant Energy also has the DLIP, which permits the grant of cash-based long-term performance-based awards, including performance units and restricted cash awards, to certain key employees. At December 31, 2015, performance units and performance-contingent cash awards were outstanding under the DLIP. There is no limit to the number of grants that can be made under the DLIP and Alliant Energy satisfies all payouts under the DLIP through cash payments. A summary of compensation expense (including amounts allocated to IPL and WPL) and the related income tax benefits recognized for share-based compensation awards was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Compensation expense |  | $10.7 |  |  |  | $15.3 |  |  |  | $12.0 |  |  |  | $5.7 |  |  |  | $8.3 |  |  |  | $6.2 |  |  |  | $4.7 |  |  |  | $6.4 |  |  |  | $5.2 |
Income tax benefits | 4.4 |  |  | 6.2 |  |  | 4.8 |  |  | 2.4 |  |  | 3.4 |  |  | 2.5 |  |  | 1.9 |  |  | 2.6 |  |  | 2.1 |
As of December 31, 2015, total unrecognized compensation cost related to share-based compensation awards was $3.9 million, which is expected to be recognized over a weighted average period of between 1 and 2 years. Share-based compensation expense is recognized on a straight-line basis over the requisite service periods and is primarily recorded in “Other operation and maintenance” in the income statements. Performance Shares and Units - Payouts of performance shares and units to key employees are contingent upon achievement over 3-year periods of specified performance criteria, which currently include metrics of total shareowner return relative to an investor-owned utility peer group. Payouts of nonvested performance shares and units are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of performance shares and units to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested performance shares and units are forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. Nonvested performance shares and units do not have non-forfeitable rights to dividends when dividends are paid to common shareowners. Alliant Energy assumes it will make future payouts of its performance shares and units in cash; therefore, performance shares and units are accounted for as liability awards. Performance Shares - Performance shares can be paid out in shares of Alliant Energy’s common stock, cash or a combination of cash and stock. Each performance share’s value is based on the closing market price of one share of Alliant Energy’s common stock at the end of the performance period. The actual number of shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares. A summary of the performance shares activity, with share amounts representing the target number of performance shares, was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested shares, January 1 | 144,424 |  |  | 139,940 |  |  | 145,277 |
Granted | 45,403 |  |  | 51,221 |  |  | 49,093 |
Vested | (45,612 | ) |  | (45,235 | ) |  | (54,430 | )
Forfeited | — |  |  | (1,502 | ) |  | — |
Nonvested shares, December 31 | 144,215 |  |  | 144,424 |  |  | 139,940 |
Certain performance shares vested, resulting in payouts (a combination of cash and common stock) as follows:
| 2015 |  | 2014 |  | 2013
| 2012 Grant |  | 2011 Grant |  | 2010 Grant
Performance shares vested | 45,612 |  |  | 45,235 |  |  | 54,430 |
Percentage of target number of performance shares | 167.5 | % |  | 147.5 | % |  | 197.5 | %
Aggregate payout value (in millions) |  | $5.1 |  |  |  | $3.4 |  |  |  | $4.8 |
Payout - cash (in millions) |  | $3.2 |  |  |  | $2.9 |  |  |  | $4.4 |
Payout - common stock shares issued | 10,975 |  |  | 4,810 |  |  | 4,177 |
Performance Units - Performance units must be paid out in cash. Each performance unit’s value is based on the average price of one share of Alliant Energy’s common stock on the grant date of the award. The actual payout for performance units is dependent upon actual performance and may range from zero to 200% of the target number of units. A summary of the performance unit activity, with amounts representing the target number of performance units, was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested units, January 1 | 63,665 |  |  | 65,912 |  |  | 64,969 |
Granted | 17,837 |  |  | 20,422 |  |  | 22,201 |
Vested | (22,845 | ) |  | (20,751 | ) |  | (19,760 | )
Forfeited | (451 | ) |  | (1,918 | ) |  | (1,498 | )
Nonvested units, December 31 | 58,206 |  |  | 63,665 |  |  | 65,912 |
Certain performance units vested, resulting in cash payouts as follows:
| 2015 |  | 2014 |  | 2013
| 2012 Grant |  | 2011 Grant |  | 2010 Grant
Performance units vested | 22,845 |  |  | 20,751 |  |  | 19,760 |
Percentage of target number of performance units | 167.5 | % |  | 147.5 | % |  | 197.5 | %
Payout value (in millions) |  | $1.6 |  |  |  | $1.2 |  |  |  | $1.3 |
Fair Value of Awards - Information related to fair values of nonvested performance shares and units at December 31, 2015, by year of grant, were as follows:
| Performance Shares |  | Performance Units
| 2015 Grant |  | 2014 Grant |  | 2013 Grant |  | 2015 Grant |  | 2014 Grant |  | 2013 Grant
Nonvested awards | 45,403 |  |  | 49,719 |  |  | 49,093 |  |  | 17,386 |  |  | 19,440 |  |  | 21,380 |
Alliant Energy common stock closing price on December 31, 2015 |  | $62.45 |  |  |  | $62.45 |  |  |  | $62.45 |  |  |  |  |  |  |
Alliant Energy common stock closing price on grant date |  |  |  |  |  |  |  | $65.09 |  |  |  | $53.77 |  |  |  | $47.58 |
Estimated payout percentage based on performance criteria | 80 | % |  | 125 | % |  | 165 | % |  | 80 | % |  | 125 | % |  | 165 | %
Fair values of each nonvested award |  | $49.96 |  |  |  | $78.06 |  |  |  | $103.04 |  |  |  | $52.07 |  |  |  | $67.21 |  |  |  | $78.51 |
At December 31, 2015, fair values of nonvested performance shares and units were calculated based on Alliant Energy’s stock price and anticipated total shareowner returns of Alliant Energy and its investor-owned utility peer group over the performance period. The portion of the fair values based on anticipated total shareowner returns was estimated using a model that incorporates the probability of meeting performance targets based on historical returns relative to the peer group. Performance-Contingent Restricted Stock - Vesting of performance-contingent restricted stock grants are based on the achievement of certain performance targets (currently specified growth of consolidated income from continuing operations). If performance targets are not met within the performance period, which currently ranges from two to four years, these restricted stock grants are forfeited. Payouts of nonvested performance-contingent restricted stock are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of performance-contingent restricted stock to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested performance-contingent restricted stock is forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. The fair value of performance-contingent restricted stock is based on the closing market price on the grant date. A summary of the performance-contingent restricted stock activity was as follows:
| 2015 |  | 2014 |  | 2013
| Shares |  | Weighted Average Fair Value |  | Shares |  | Weighted Average Fair Value |  | Shares |  | Weighted Average Fair Value
Nonvested shares, January 1 | 98,812 |  |  |  | $50.69 |  |  | 158,922 |  |  |  | $42.71 |  |  | 211,651 |  |  |  | $32.42 |
Granted | 45,403 |  |  | 65.09 |  |  | 51,221 |  |  | 53.77 |  |  | 49,093 |  |  | 47.58 |
Vested (a) | (49,093 | ) |  | 47.58 |  |  | (90,847 | ) |  | 40.91 |  |  | — |  |  | — |
Forfeited (b) | — |  |  | — |  |  | (20,484 | ) |  | 39.85 |  |  | (101,822 | ) |  | 23.67 |
Nonvested shares, December 31 | 95,122 |  |  | 59.17 |  |  | 98,812 |  |  | 50.69 |  |  | 158,922 |  |  | 42.71 |
(a) | In 2015, 49,093 performance-contingent restricted shares granted in 2013 vested because the specified performance criteria for such shares were met. In 2014, 45,612 and 45,235 performance-contingent restricted shares granted in 2012 and 2011, respectively, vested because the specified performance criteria for such shares were met.
(b) | In 2013, 101,822 performance-contingent restricted shares granted in 2009 were forfeited because the specified performance criteria for such shares were not met. The forfeitures during 2014 were primarily caused by retirements and terminations of participants.
Performance-Contingent Cash Awards - Performance-contingent cash award payouts to key employees are based on the achievement of certain performance targets (currently specified growth of consolidated income from continuing operations). If performance targets are not met within the performance period, which currently ranges from two to four years, there are no payouts for these awards. Payouts of nonvested awards are based on achievement of the performance criteria and are prorated in the event of retirement, death or disability during the first year of the performance period based on time worked during the first year of the performance period, and are prorated upon involuntary termination without cause based on time worked during the entire performance period. Upon achievement of the performance criteria, payouts of these awards to participants who terminate employment after the first year of the performance period due to retirement, death or disability are not prorated. Participants’ nonvested awards are forfeited if the participant voluntarily leaves Alliant Energy or is terminated for cause during the performance period. Each performance-contingent cash award’s value is based on the price of one share of Alliant Energy’s common stock at the end of the performance period. Alliant Energy accounts for performance-contingent cash awards as liability awards because payouts will be made in the form of cash. A summary of the performance-contingent cash awards activity was as follows:
| 2015 |  | 2014 |  | 2013
Nonvested awards, January 1 | 78,930 |  |  | 96,977 |  |  | 59,639 |
Granted | 41,105 |  |  | 42,446 |  |  | 39,530 |
Vested (a) | (37,332 | ) |  | (55,517 | ) |  | — |
Forfeited | (827 | ) |  | (4,976 | ) |  | (2,192 | )
Nonvested awards, December 31 | 81,876 |  |  | 78,930 |  |  | 96,977 |
(a) | In 2015, 37,332 performance-contingent cash awards granted in 2013 vested, resulting in cash payouts valued at $2.4 million. In 2014, 34,766 and 20,751 performance-contingent cash awards granted in 2012 and 2011 vested, resulting in cash payouts valued at $1.9 million and $1.1 million, respectively.

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