XML 77 R44.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Retirement Benefits (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items] |
Schedule Of SERP Trust Assets, ABO And Contributions | Presented in the following table are the fair values of trust assets, ABO, and contributions for CMS Energy’s and Consumers’ DB SERP:
In Millions |
Years Ended December 31 | 2018 |  | 2017 |
CMS Energy, including Consumers |  |  |  |
Trust assets |  | $ | 147 |  |  | $ | 146 |
ABO |  | 137 |  |  | 149 |
Contributions |  | 8 |  |  | 7 |
Consumers |  |  |  |
Trust assets |  | $ | 106 |  |  | $ | 106 |
ABO |  | 98 |  |  | 107 |
Contributions |  | 5 |  |  | 6 |
Schedule Of Effect Of One-Percentage-Point Change In Assumed Health Care Cost Trend Rates | Presented in the following table are the effects of a one-percentage-point change in the health care cost-trend assumption:
In Millions |
Year Ended December 31, 2018 | One Percentage Point Increase |  | One Percentage Point Decrease |
CMS Energy, including Consumers |  |  |  |
Effect on total service and interest cost component |  | $ | 2 |  |  | $ | (2 | )
Effect on PBO |  | 30 |  |  | (26 | )
Consumers |  |  |  |
Effect on total service and interest cost component |  | $ | 2 |  |  | $ | (2 | )
Effect on PBO |  | 28 |  |  | (25 | )
Schedule Of Assumptions Used | Presented in the following table are the weighted-average assumptions used in CMS Energy’s and Consumers’ retirement benefits plans to determine benefit obligations and net periodic benefit cost:
December 31 | 2018 |  | 2017 |  | 2016 |
CMS Energy, including Consumers |  |  |
Weighted average for benefit obligations 1 |  |  |
Discount rate 2 |  |  |
DB Pension Plan A 3 | 4.48 | % | 3.78 | % |
DB Pension Plan B 3 | 4.32 |  | 3.64 |  |
DB SERP | 4.32 |  | 3.65 |  | 4.16 | %
OPEB Plan | 4.42 |  | 3.74 |  | 4.49 |
Rate of compensation increase |  |  |
DB Pension Plan A 3 | 3.50 |  | 3.50 |  |
DB SERP | 5.50 |  | 5.50 |  | 5.50 |
Weighted average for net periodic benefit cost 1 |  |  |
Service cost discount rate 2,4 |  |  |
DB Pension Plan A 3 | 3.85 |  |  |  |  |
DB SERP | 3.83 |  | 4.51 |  | 4.87 |
OPEB Plan | 3.93 |  | 4.89 |  | 4.75 |
Interest cost discount rate 2,4 |  |  |
DB Pension Plan A 3 | 3.39 |  |  |
DB Pension Plan B 3 | 3.24 |  |  |  |  |
DB SERP | 3.26 |  | 3.51 |  | 3.64 |
OPEB Plan | 3.35 |  | 3.79 |  | 3.89 |
Expected long-term rate of return on plan assets 5 |  |  |
DB Pension Plans | 7.00 |  | 7.25 |  | 7.25 |
OPEB Plan | 7.00 |  | 7.25 |  | 7.25 |
Rate of compensation increase |  |  |
DB Pension Plan A 3 | 3.50 |  |  |  |  |
DB SERP | 5.50 |  | 5.50 |  | 5.50 |
1 | The mortality assumption for benefit obligations was based on the RP-2014 mortality table, with projection scales MP-2018 for 2018, MP-2017 for 2017, and MP-2016 for 2016. The mortality assumption for net periodic benefit cost for 2018, 2017, and 2016 was based on the RP-2014 mortality table, with projection scales MP-2017 for 2018, MP-2016 for 2017, and MP-2015 for 2016.
2 | The discount rate reflects the rate at which benefits could be effectively settled and is equal to the equivalent single rate resulting from a yield-curve analysis. This analysis incorporated the projected benefit payments specific to CMS Energy’s and Consumers’ DB Pension Plans and OPEB Plan and the yields on high-quality corporate bonds rated Aa or better.
3 | Effective December 31, 2017, CMS Energy’s and Consumers’ existing defined benefit pension plan was amended to include only retired or inactive employees; this amended plan is referred to as DB Pension Plan B. Active employees were moved to a newly created pension plan, referred to as DB Pension Plan A.
The assumptions used to measure the plan obligation of the previous defined benefit pension plan at December 31, 2016 were:
• | discount rate of 4.30 percent
• | weighted-average rate of compensation increase of 3.60 percent
The assumptions used to measure the plan cost of the previous defined benefit pension plan were:
• | service cost discount rate of 4.53 percent at December 31, 2017 and 4.79 percent at December 31, 2016
• | interest cost discount rate of 3.56 percent at December 31, 2017 and 3.66 percent at December 31, 2016
• | weighted-average rate of compensation increase of 3.60 percent at December 31, 2017 and 3.00 percent at December 31, 2016
4 | In 2016, CMS Energy and Consumers changed the method they use to determine the discount rate used to calculate the service cost and interest cost components of net periodic benefit costs for the DB Pension and OPEB Plans. Historically, the discount rate used for this purpose represented a single weighted-average rate derived from the yield curve used to determine the benefit obligation. CMS Energy and Consumers have elected to use instead a full-yield-curve approach in the estimation of service cost and interest cost; this approach is more accurate in that it applies individual spot rates along the yield curve to future projected benefit payments based on the time of payment.
5 | CMS Energy and Consumers determined the long-term rate of return using historical market returns, the present and expected future economic environment, the capital market principles of risk and return, and the expert opinions of individuals and firms with financial market knowledge. CMS Energy and Consumers considered the asset allocation of the portfolio in forecasting the future expected total return of the portfolio. The goal was to determine a long-term rate of return that could be incorporated into the planning of future cash flow requirements in conjunction with the change in the liability. Annually, CMS Energy and Consumers review for reasonableness and appropriateness the forecasted returns for various classes of assets used to construct an expected return model. CMS Energy’s and Consumers’ expected long-term rate of return on the assets of the DB Pension Plans was 7.00 percent in 2018. The actual return (loss) on the assets of the DB Pension Plans was (6.7) percent in 2018, 18.0 percent in 2017, and 8.0 percent in 2016.
Schedule Of Net Benefit Costs | Presented in the following table are the costs (credits) and other changes in plan assets and benefit obligations incurred in CMS Energy’s and Consumers’ retirement benefits plans:
In Millions |
| DB Pension Plans and DB SERP |  | OPEB Plan
Years Ended December 31 | 2018 |  | 2017 |  | 2016 |  |  | 2018 |  | 2017 |  | 2016 |
CMS Energy, including Consumers |  |  |  |  |  |  |  |  |  |  |  |  |
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 48 |  |  | $ | 45 |  |  | $ | 42 |  |  |  | $ | 17 |  |  | $ | 19 |  |  | $ | 18 |
Interest cost |  | 95 |  |  | 93 |  |  | 90 |  |  |  | 34 |  |  | 51 |  |  | 46 |
Expected return on plan assets |  | (149 | ) |  | (153 | ) |  | (147 | ) |  |  | (97 | ) |  | (90 | ) |  | (85 | )
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 76 |  |  | 82 |  |  | 71 |  |  |  | 15 |  |  | 29 |  |  | 21 |
Prior service cost (credit) |  | 3 |  |  | 5 |  |  | 4 |  |  |  | (67 | ) |  | (40 | ) |  | (41 | )
Net periodic cost (credit) |  | $ | 73 |  |  | $ | 72 |  |  | $ | 60 |  |  |  | $ | (98 | ) |  | $ | (31 | ) |  | $ | (41 | )
Consumers |  |  |  |  |  |  |  |  |  |  |  |  |
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 47 |  |  | $ | 44 |  |  | $ | 41 |  |  |  | $ | 16 |  |  | $ | 19 |  |  | $ | 17 |
Interest cost |  | 88 |  |  | 90 |  |  | 87 |  |  |  | 33 |  |  | 49 |  |  | 45 |
Expected return on plan assets |  | (139 | ) |  | (149 | ) |  | (143 | ) |  |  | (91 | ) |  | (84 | ) |  | (80 | )
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 73 |  |  | 79 |  |  | 68 |  |  |  | 16 |  |  | 29 |  |  | 22 |
Prior service cost (credit) |  | 3 |  |  | 4 |  |  | 4 |  |  |  | (65 | ) |  | (39 | ) |  | (40 | )
Net periodic cost (credit) |  | $ | 72 |  |  | $ | 68 |  |  | $ | 57 |  |  |  | $ | (91 | ) |  | $ | (26 | ) |  | $ | (36 | )
Schedule Of Net Loss And Prior Service Cost (Credit) That Will Be Amortized In Next Fiscal Year | Presented in the following table are the estimated net loss and prior service cost (credit) that will be amortized into net periodic benefit cost in 2019 from or to the associated regulatory asset and AOCI:
In Millions |
| DB Pension Plans |  | OPEB Plan |
CMS Energy, including Consumers |  |  |  |
Regulatory asset |  | $ | 47 |  |  | $ | (35 | )
AOCI |  | 3 |  |  | (1 | )
Consumers |  |  |  |
Regulatory asset |  | $ | 47 |  |  | $ | (35 | )
Schedule Of Funded Status Of Retirement Benefit Plans | Presented in the following table are reconciliations of the funded status of CMS Energy’s and Consumers’ retirement benefits plans with their retirement benefits plans’ liabilities:
In Millions
| DB Pension Plans |  | DB SERP |  | OPEB Plan
Years Ended December 31 | 2018 |  | 2017 |  |  | 2018 |  | 2017 |  |  | 2018 |  | 2017 |  |
CMS Energy, including Consumers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of period |  | $ | 2,780 |  |  | $ | 2,562 |  |  |  | $ | 154 |  |  | $ | 151 |  |  |  | $ | 1,097 |  |  | $ | 1,408 |  |
Service cost |  | 48 |  |  | 45 |  |  |  | — |  |  | — |  |  |  | 17 |  |  | 19 |  |
Interest cost |  | 90 |  |  | 88 |  |  |  | 5 |  |  | 5 |  |  |  | 34 |  |  | 51 |  |
Plan amendments |  | — |  |  | — |  |  |  | — |  |  | — |  |  |  | 26 |  |  | (309 | ) |
Actuarial (gain) loss |  | (258 | ) | 1 | 241 |  | 1 |  | (10 | ) |  | 7 |  |  |  | (74 | ) | 1 | (24 | ) | 1
Benefits paid |  | (148 | ) |  | (156 | ) |  |  | (9 | ) |  | (9 | ) |  |  | (55 | ) |  | (48 | ) |
Benefit obligation at end of period |  | $ | 2,512 |  |  | $ | 2,780 |  |  |  | $ | 140 |  |  | $ | 154 |  |  |  | $ | 1,045 |  |  | $ | 1,097 |  |
Plan assets at fair value at beginning of period |  | $ | 2,305 |  |  | $ | 2,101 |  |  |  | $ | — |  |  | $ | — |  |  |  | $ | 1,420 |  |  | $ | 1,264 |  |
Actual return on plan assets |  | (150 | ) |  | 360 |  |  |  | — |  |  | — |  |  |  | (86 | ) |  | 203 |  |
Company contribution |  | 240 |  |  | — |  |  |  | 9 |  |  | 9 |  |  |  | — |  |  | — |  |
Actual benefits paid |  | (148 | ) |  | (156 | ) |  |  | (9 | ) |  | (9 | ) |  |  | (54 | ) |  | (47 | ) |
Plan assets at fair value at end of period |  | $ | 2,247 |  |  | $ | 2,305 |  |  |  | $ | — |  |  | $ | — |  |  |  | $ | 1,280 |  |  | $ | 1,420 |  |
Funded status |  | $ | (265 | ) | 2 | $ | (475 | ) | 2 |  | $ | (140 | ) |  | $ | (154 | ) |  |  | $ | 235 |  |  | $ | 323 |  |
Consumers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of period |  |  |  |  |  |  | $ | 112 |  |  | $ | 109 |  |  |  | $ | 1,053 |  |  | $ | 1,365 |  |
Service cost |  |  |  |  |  |  | — |  |  | — |  |  |  | 16 |  |  | 19 |  |
Interest cost |  |  |  |  |  |  | 4 |  |  | 4 |  |  |  | 33 |  |  | 49 |  |
Plan amendments |  |  |  |  |  |  | — |  |  | — |  |  |  | 25 |  |  | (303 | ) |
Actuarial (gain) loss |  |  |  |  |  |  | (8 | ) |  | 5 |  |  |  | (70 | ) | 1 | (31 | ) | 1
Benefits paid |  |  |  |  |  |  | (7 | ) |  | (6 | ) |  |  | (53 | ) |  | (46 | ) |
Benefit obligation at end of period |  |  |  |  |  |  | $ | 101 |  |  | $ | 112 |  |  |  | $ | 1,004 |  |  | $ | 1,053 |  |
Plan assets at fair value at beginning of period |  |  |  |  |  |  | $ | — |  |  | $ | — |  |  |  | $ | 1,329 |  |  | $ | 1,184 |  |
Actual return on plan assets |  |  |  |  |  |  | — |  |  | — |  |  |  | (80 | ) |  | 190 |  |
Company contribution |  |  |  |  |  |  | 7 |  |  | 6 |  |  |  | — |  |  | — |  |
Actual benefits paid |  |  |  |  |  |  | (7 | ) |  | (6 | ) |  |  | (52 | ) |  | (45 | ) |
Plan assets at fair value at end of period |  |  |  |  |  |  | $ | — |  |  | $ | — |  |  |  | $ | 1,197 |  |  | $ | 1,329 |  |
Funded status |  |  |  |  |  |  | $ | (101 | ) |  | $ | (112 | ) |  |  | $ | 193 |  |  | $ | 276 |  |
1 | The actuarial gain for 2018 for the DB Pension Plans was primarily the result of higher discount rates. The actuarial loss for 2017 was primarily the result of lower discount rates. The actuarial gain for 2018 for the OPEB Plan was primarily the result of higher discount rates. The actuarial gain for 2017 was primarily the result of better claim experience in calculating the plan’s funded status.
2 | At December 31, 2018, $246 million of the total funded status of the DB Pension Plans was attributable to Consumers, based on an allocation of expenses. At December 31, 2017, $455 million of the total funded status of the DB Pension Plans was attributable to Consumers, based on an allocation of expenses.
Schedule Of Retirement Benefit Plan Assets (Liabilities) | Presented in the following table is the classification of CMS Energy’s and Consumers’ retirement benefit plans’ assets and liabilities:
In Millions |
December 31 | 2018 |  | 2017 |
CMS Energy, including Consumers |  |  |  |
Non-current assets |  |  |  |
DB Pension Plans |  | $ | 38 |  |  | $ | 143 |
OPEB Plan |  | 235 |  |  | 323 |
Current liabilities |  |  |  |
DB SERP |  | 10 |  |  | 9 |
Non-current liabilities |  |  |  |  |  |
DB Pension Plans |  | 303 |  |  | 618 |
DB SERP |  | 130 |  |  | 145 |
Consumers |  |  |  |
Non-current assets |  |  |  |
DB Pension Plans |  | $ | 49 |  |  | $ | 147 |
OPEB Plan |  | 193 |  |  | 276 |
Current liabilities |  |  |  |
DB SERP |  | 7 |  |  | 7 |
Non-current liabilities |  |  |  |  |  |
DB Pension Plans |  | 295 |  |  | 602 |
DB SERP |  | 94 |  |  | 105 |
Schedule Of Accumulated And Projected Benefit Obligations | Presented in the following table is information related to the defined benefit pension plan for which the PBO and the ABO exceed plan assets:
In Millions |
December 31 |  | 2018 |  |  | 2017 |
CMS Energy, including Consumers |  |  |  |
PBO |  | $ | 1,363 |  |  | $ | 1,511 |
ABO |  | 1,091 |  |  | 1,164 |
Fair value of plan assets |  | 1,059 |  |  | 893 |
Schedule Of Net Periodic Benefit Cost Not Yet Recognized | For additional details on regulatory assets and liabilities, see Note 3, Regulatory Matters.
In Millions |
| DB Pension Plans and DB SERP |  | OPEB Plan
Years Ended December 31 | 2018 |  | 2017 |  |  | 2018 |  | 2017 |
CMS Energy, including Consumers |  |  |  |  |  |  |  |  |
Regulatory assets (liabilities) |  |  |  |  |  |  |  |  |
Net loss |  | $ | 978 |  |  | $ | 1,017 |  |  |  | $ | 402 |  |  | $ | 316 |
Prior service cost (credit) |  | 9 |  |  | 11 |  |  |  | (361 | ) |  | (451 | )
Regulatory assets (liabilities) |  | $ | 987 |  |  | $ | 1,028 |  |  |  | $ | 41 |  |  | $ | (135 | )
AOCI |  |  |  |  |  |  |  |  |
Net loss (gain) |  | 90 |  |  | 97 |  |  |  | 2 |  |  | (6 | )
Prior service cost (credit) |  | — |  |  | 1 |  |  |  | (9 | ) |  | (12 | )
Total amounts recognized in regulatory assets (liabilities) and AOCI |  | $ | 1,077 |  |  | $ | 1,126 |  |  |  | $ | 34 |  |  | $ | (153 | )
Consumers |  |  |  |  |  |  |  |  |
Regulatory assets (liabilities) |  |  |  |  |  |  |  |  |
Net loss |  | $ | 978 |  |  | $ | 1,017 |  |  |  | $ | 402 |  |  | $ | 316 |
Prior service cost (credit) |  | 9 |  |  | 11 |  |  |  | (361 | ) |  | (451 | )
Regulatory assets (liabilities) |  | $ | 987 |  |  | $ | 1,028 |  |  |  | $ | 41 |  |  | $ | (135 | )
AOCI |  |  |  |  |  |  |  |  |
Net loss |  | 27 |  |  | 36 |  |  |  | — |  |  | — |
Total amounts recognized in regulatory assets (liabilities) and AOCI |  | $ | 1,014 |  |  | $ | 1,064 |  |  |  | $ | 41 |  |  | $ | (135 | )
Schedule Of Allocation Of Plan Assets | For additional details regarding the fair value hierarchy, see Note 6, Fair Value Measurements.
In Millions |
| DB Pension Plans
| December 31, 2018 |  | December 31, 2017
| Total |  | Level 1 |  | Level 2 |  |  | Total |  | Level 1 |  | Level 2 |
CMS Energy, including Consumers |  |  |  |  |  |  |  |  |  |  |  |  |
Cash and short-term investments |  | $ | 242 |  |  | $ | 242 |  |  | $ | — |  |  |  | $ | 21 |  |  | $ | 21 |  |  | $ | — |
U.S. government and agencies securities |  | 11 |  |  | — |  |  | 11 |  |  |  | 4 |  |  | — |  |  | 4 |
Corporate debt |  | 400 |  |  | — |  |  | 400 |  |  |  | 336 |  |  | — |  |  | 336 |
State and municipal bonds |  | 6 |  |  | — |  |  | 6 |  |  |  | 9 |  |  | — |  |  | 9 |
Foreign corporate bonds |  | 35 |  |  | — |  |  | 35 |  |  |  | 31 |  |  | — |  |  | 31 |
Mutual funds |  | 552 |  |  | 552 |  |  | — |  |  |  | 662 |  |  | 662 |  |  | — |
|  | $ | 1,246 |  |  | $ | 794 |  |  | $ | 452 |  |  |  | $ | 1,063 |  |  | $ | 683 |  |  | $ | 380 |
Pooled funds |  | 1,001 |  |  |  |  |  |  |  | 1,242 |  |  |  |  |
Total |  | $ | 2,247 |  |  |  |  |  |  |  | $ | 2,305 |  |  |  |  |
In Millions |
| OPEB Plan
| December 31, 2018 |  | December 31, 2017
| Total |  | Level 1 |  | Level 2 |  |  | Total |  | Level 1 |  | Level 2 |
CMS Energy, including Consumers |  |  |  |  |  |  |  |  |  |  |  |  |
Cash and short-term investments |  | $ | 36 |  |  | $ | 36 |  |  | $ | — |  |  |  | $ | 16 |  |  | $ | 16 |  |  | $ | — |
U.S. government and agencies securities |  | 2 |  |  | — |  |  | 2 |  |  |  | 1 |  |  | — |  |  | 1 |
Corporate debt |  | 55 |  |  | — |  |  | 55 |  |  |  | 50 |  |  | — |  |  | 50 |
State and municipal bonds |  | 1 |  |  | — |  |  | 1 |  |  |  | 1 |  |  | — |  |  | 1 |
Foreign corporate bonds |  | 5 |  |  | — |  |  | 5 |  |  |  | 4 |  |  | — |  |  | 4 |
Common stocks |  | 41 |  |  | 41 |  |  | — |  |  |  | 40 |  |  | 40 |  |  | — |
Mutual funds |  | 594 |  |  | 594 |  |  | — |  |  |  | 647 |  |  | 647 |  |  | — |
|  | $ | 734 |  |  | $ | 671 |  |  | $ | 63 |  |  |  | $ | 759 |  |  | $ | 703 |  |  | $ | 56 |
Pooled funds |  | 546 |  |  |  |  |  |  |  | 661 |  |  |  |  |
Total |  | $ | 1,280 |  |  |  |  |  |  |  | $ | 1,420 |  |  |  |  |
Schedule Of Asset Allocation | Asset Allocations: Presented in the following table are the investment components of the assets of CMS Energy’s DB Pension Plans and OPEB Plan as of December 31, 2018:
| DB Pension Plans |  | OPEB Plan |
Equity securities |  | 52 | % |  | 50 | %
Fixed-income securities |  | 42 |  |  | 31 |
Multi-asset investments |  | 6 |  |  | 19 |
|  | 100 | % |  | 100 | %
Schedule Of Plan Contributions | Presented in the following table are the contributions to CMS Energy’s and Consumers’ OPEB Plan and DB Pension Plans:
In Millions |
Years Ended December 31 | 2018 |  | 2017 |
CMS Energy, including Consumers |  |  |  |
OPEB Plan |  | $ | — |  |  | $ | — |
DB Pension Plans |  | 240 |  |  | — |
Consumers |  |  |  |
OPEB Plan |  | $ | — |  |  | $ | — |
DB Pension Plans |  | 234 |  |  | — |
Schedule Of Expected Benefit Payments | Presented in the following table are the expected benefit payments for each of the next five years and the five-year period thereafter:
In Millions |
| DB Pension Plans |  | DB SERP |  | OPEB Plan |
CMS Energy, including Consumers |  |  |  |  |  |
2019 |  | $ | 159 |  |  | $ | 10 |  |  | $ | 59 |
2020 |  | 162 |  |  | 10 |  |  | 61 |
2021 |  | 164 |  |  | 10 |  |  | 64 |
2022 |  | 165 |  |  | 10 |  |  | 65 |
2023 |  | 165 |  |  | 10 |  |  | 66 |
2024-2028 |  | 823 |  |  | 46 |  |  | 328 |
Consumers |  |  |  |  |  |
2019 |  | $ | 149 |  |  | $ | 7 |  |  | $ | 57 |
2020 |  | 152 |  |  | 7 |  |  | 59 |
2021 |  | 154 |  |  | 7 |  |  | 61 |
2022 |  | 155 |  |  | 7 |  |  | 62 |
2023 |  | 155 |  |  | 7 |  |  | 63 |
2024-2028 |  | 777 |  |  | 31 |  |  | 315 |
Consumers Energy Company |
Defined Benefit Plan Disclosure [Line Items] |
Schedule Of SERP Trust Assets, ABO And Contributions | Presented in the following table are the fair values of trust assets, ABO, and contributions for CMS Energy’s and Consumers’ DB SERP:
In Millions |
Years Ended December 31 | 2018 |  | 2017 |
CMS Energy, including Consumers |  |  |  |
Trust assets |  | $ | 147 |  |  | $ | 146 |
ABO |  | 137 |  |  | 149 |
Contributions |  | 8 |  |  | 7 |
Consumers |  |  |  |
Trust assets |  | $ | 106 |  |  | $ | 106 |
ABO |  | 98 |  |  | 107 |
Contributions |  | 5 |  |  | 6 |
Schedule Of Effect Of One-Percentage-Point Change In Assumed Health Care Cost Trend Rates | Presented in the following table are the effects of a one-percentage-point change in the health care cost-trend assumption:
In Millions |
Year Ended December 31, 2018 | One Percentage Point Increase |  | One Percentage Point Decrease |
CMS Energy, including Consumers |  |  |  |
Effect on total service and interest cost component |  | $ | 2 |  |  | $ | (2 | )
Effect on PBO |  | 30 |  |  | (26 | )
Consumers |  |  |  |
Effect on total service and interest cost component |  | $ | 2 |  |  | $ | (2 | )
Effect on PBO |  | 28 |  |  | (25 | )
Schedule Of Assumptions Used | Presented in the following table are the weighted-average assumptions used in CMS Energy’s and Consumers’ retirement benefits plans to determine benefit obligations and net periodic benefit cost:
December 31 | 2018 |  | 2017 |  | 2016 |
CMS Energy, including Consumers |  |  |
Weighted average for benefit obligations 1 |  |  |
Discount rate 2 |  |  |
DB Pension Plan A 3 | 4.48 | % | 3.78 | % |
DB Pension Plan B 3 | 4.32 |  | 3.64 |  |
DB SERP | 4.32 |  | 3.65 |  | 4.16 | %
OPEB Plan | 4.42 |  | 3.74 |  | 4.49 |
Rate of compensation increase |  |  |
DB Pension Plan A 3 | 3.50 |  | 3.50 |  |
DB SERP | 5.50 |  | 5.50 |  | 5.50 |
Weighted average for net periodic benefit cost 1 |  |  |
Service cost discount rate 2,4 |  |  |
DB Pension Plan A 3 | 3.85 |  |  |  |  |
DB SERP | 3.83 |  | 4.51 |  | 4.87 |
OPEB Plan | 3.93 |  | 4.89 |  | 4.75 |
Interest cost discount rate 2,4 |  |  |
DB Pension Plan A 3 | 3.39 |  |  |
DB Pension Plan B 3 | 3.24 |  |  |  |  |
DB SERP | 3.26 |  | 3.51 |  | 3.64 |
OPEB Plan | 3.35 |  | 3.79 |  | 3.89 |
Expected long-term rate of return on plan assets 5 |  |  |
DB Pension Plans | 7.00 |  | 7.25 |  | 7.25 |
OPEB Plan | 7.00 |  | 7.25 |  | 7.25 |
Rate of compensation increase |  |  |
DB Pension Plan A 3 | 3.50 |  |  |  |  |
DB SERP | 5.50 |  | 5.50 |  | 5.50 |
1 | The mortality assumption for benefit obligations was based on the RP-2014 mortality table, with projection scales MP-2018 for 2018, MP-2017 for 2017, and MP-2016 for 2016. The mortality assumption for net periodic benefit cost for 2018, 2017, and 2016 was based on the RP-2014 mortality table, with projection scales MP-2017 for 2018, MP-2016 for 2017, and MP-2015 for 2016.
2 | The discount rate reflects the rate at which benefits could be effectively settled and is equal to the equivalent single rate resulting from a yield-curve analysis. This analysis incorporated the projected benefit payments specific to CMS Energy’s and Consumers’ DB Pension Plans and OPEB Plan and the yields on high-quality corporate bonds rated Aa or better.
3 | Effective December 31, 2017, CMS Energy’s and Consumers’ existing defined benefit pension plan was amended to include only retired or inactive employees; this amended plan is referred to as DB Pension Plan B. Active employees were moved to a newly created pension plan, referred to as DB Pension Plan A.
The assumptions used to measure the plan obligation of the previous defined benefit pension plan at December 31, 2016 were:
• | discount rate of 4.30 percent
• | weighted-average rate of compensation increase of 3.60 percent
The assumptions used to measure the plan cost of the previous defined benefit pension plan were:
• | service cost discount rate of 4.53 percent at December 31, 2017 and 4.79 percent at December 31, 2016
• | interest cost discount rate of 3.56 percent at December 31, 2017 and 3.66 percent at December 31, 2016
• | weighted-average rate of compensation increase of 3.60 percent at December 31, 2017 and 3.00 percent at December 31, 2016
4 | In 2016, CMS Energy and Consumers changed the method they use to determine the discount rate used to calculate the service cost and interest cost components of net periodic benefit costs for the DB Pension and OPEB Plans. Historically, the discount rate used for this purpose represented a single weighted-average rate derived from the yield curve used to determine the benefit obligation. CMS Energy and Consumers have elected to use instead a full-yield-curve approach in the estimation of service cost and interest cost; this approach is more accurate in that it applies individual spot rates along the yield curve to future projected benefit payments based on the time of payment.
5 | CMS Energy and Consumers determined the long-term rate of return using historical market returns, the present and expected future economic environment, the capital market principles of risk and return, and the expert opinions of individuals and firms with financial market knowledge. CMS Energy and Consumers considered the asset allocation of the portfolio in forecasting the future expected total return of the portfolio. The goal was to determine a long-term rate of return that could be incorporated into the planning of future cash flow requirements in conjunction with the change in the liability. Annually, CMS Energy and Consumers review for reasonableness and appropriateness the forecasted returns for various classes of assets used to construct an expected return model. CMS Energy’s and Consumers’ expected long-term rate of return on the assets of the DB Pension Plans was 7.00 percent in 2018. The actual return (loss) on the assets of the DB Pension Plans was (6.7) percent in 2018, 18.0 percent in 2017, and 8.0 percent in 2016.
Schedule Of Net Benefit Costs | Presented in the following table are the costs (credits) and other changes in plan assets and benefit obligations incurred in CMS Energy’s and Consumers’ retirement benefits plans:
In Millions |
| DB Pension Plans and DB SERP |  | OPEB Plan
Years Ended December 31 | 2018 |  | 2017 |  | 2016 |  |  | 2018 |  | 2017 |  | 2016 |
CMS Energy, including Consumers |  |  |  |  |  |  |  |  |  |  |  |  |
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 48 |  |  | $ | 45 |  |  | $ | 42 |  |  |  | $ | 17 |  |  | $ | 19 |  |  | $ | 18 |
Interest cost |  | 95 |  |  | 93 |  |  | 90 |  |  |  | 34 |  |  | 51 |  |  | 46 |
Expected return on plan assets |  | (149 | ) |  | (153 | ) |  | (147 | ) |  |  | (97 | ) |  | (90 | ) |  | (85 | )
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 76 |  |  | 82 |  |  | 71 |  |  |  | 15 |  |  | 29 |  |  | 21 |
Prior service cost (credit) |  | 3 |  |  | 5 |  |  | 4 |  |  |  | (67 | ) |  | (40 | ) |  | (41 | )
Net periodic cost (credit) |  | $ | 73 |  |  | $ | 72 |  |  | $ | 60 |  |  |  | $ | (98 | ) |  | $ | (31 | ) |  | $ | (41 | )
Consumers |  |  |  |  |  |  |  |  |  |  |  |  |
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 47 |  |  | $ | 44 |  |  | $ | 41 |  |  |  | $ | 16 |  |  | $ | 19 |  |  | $ | 17 |
Interest cost |  | 88 |  |  | 90 |  |  | 87 |  |  |  | 33 |  |  | 49 |  |  | 45 |
Expected return on plan assets |  | (139 | ) |  | (149 | ) |  | (143 | ) |  |  | (91 | ) |  | (84 | ) |  | (80 | )
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 73 |  |  | 79 |  |  | 68 |  |  |  | 16 |  |  | 29 |  |  | 22 |
Prior service cost (credit) |  | 3 |  |  | 4 |  |  | 4 |  |  |  | (65 | ) |  | (39 | ) |  | (40 | )
Net periodic cost (credit) |  | $ | 72 |  |  | $ | 68 |  |  | $ | 57 |  |  |  | $ | (91 | ) |  | $ | (26 | ) |  | $ | (36 | )
Schedule Of Net Loss And Prior Service Cost (Credit) That Will Be Amortized In Next Fiscal Year | Presented in the following table are the estimated net loss and prior service cost (credit) that will be amortized into net periodic benefit cost in 2019 from or to the associated regulatory asset and AOCI:
In Millions |
| DB Pension Plans |  | OPEB Plan |
CMS Energy, including Consumers |  |  |  |
Regulatory asset |  | $ | 47 |  |  | $ | (35 | )
AOCI |  | 3 |  |  | (1 | )
Consumers |  |  |  |
Regulatory asset |  | $ | 47 |  |  | $ | (35 | )
Schedule Of Funded Status Of Retirement Benefit Plans | Presented in the following table are reconciliations of the funded status of CMS Energy’s and Consumers’ retirement benefits plans with their retirement benefits plans’ liabilities:
In Millions
| DB Pension Plans |  | DB SERP |  | OPEB Plan
Years Ended December 31 | 2018 |  | 2017 |  |  | 2018 |  | 2017 |  |  | 2018 |  | 2017 |  |
CMS Energy, including Consumers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of period |  | $ | 2,780 |  |  | $ | 2,562 |  |  |  | $ | 154 |  |  | $ | 151 |  |  |  | $ | 1,097 |  |  | $ | 1,408 |  |
Service cost |  | 48 |  |  | 45 |  |  |  | — |  |  | — |  |  |  | 17 |  |  | 19 |  |
Interest cost |  | 90 |  |  | 88 |  |  |  | 5 |  |  | 5 |  |  |  | 34 |  |  | 51 |  |
Plan amendments |  | — |  |  | — |  |  |  | — |  |  | — |  |  |  | 26 |  |  | (309 | ) |
Actuarial (gain) loss |  | (258 | ) | 1 | 241 |  | 1 |  | (10 | ) |  | 7 |  |  |  | (74 | ) | 1 | (24 | ) | 1
Benefits paid |  | (148 | ) |  | (156 | ) |  |  | (9 | ) |  | (9 | ) |  |  | (55 | ) |  | (48 | ) |
Benefit obligation at end of period |  | $ | 2,512 |  |  | $ | 2,780 |  |  |  | $ | 140 |  |  | $ | 154 |  |  |  | $ | 1,045 |  |  | $ | 1,097 |  |
Plan assets at fair value at beginning of period |  | $ | 2,305 |  |  | $ | 2,101 |  |  |  | $ | — |  |  | $ | — |  |  |  | $ | 1,420 |  |  | $ | 1,264 |  |
Actual return on plan assets |  | (150 | ) |  | 360 |  |  |  | — |  |  | — |  |  |  | (86 | ) |  | 203 |  |
Company contribution |  | 240 |  |  | — |  |  |  | 9 |  |  | 9 |  |  |  | — |  |  | — |  |
Actual benefits paid |  | (148 | ) |  | (156 | ) |  |  | (9 | ) |  | (9 | ) |  |  | (54 | ) |  | (47 | ) |
Plan assets at fair value at end of period |  | $ | 2,247 |  |  | $ | 2,305 |  |  |  | $ | — |  |  | $ | — |  |  |  | $ | 1,280 |  |  | $ | 1,420 |  |
Funded status |  | $ | (265 | ) | 2 | $ | (475 | ) | 2 |  | $ | (140 | ) |  | $ | (154 | ) |  |  | $ | 235 |  |  | $ | 323 |  |
Consumers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of period |  |  |  |  |  |  | $ | 112 |  |  | $ | 109 |  |  |  | $ | 1,053 |  |  | $ | 1,365 |  |
Service cost |  |  |  |  |  |  | — |  |  | — |  |  |  | 16 |  |  | 19 |  |
Interest cost |  |  |  |  |  |  | 4 |  |  | 4 |  |  |  | 33 |  |  | 49 |  |
Plan amendments |  |  |  |  |  |  | — |  |  | — |  |  |  | 25 |  |  | (303 | ) |
Actuarial (gain) loss |  |  |  |  |  |  | (8 | ) |  | 5 |  |  |  | (70 | ) | 1 | (31 | ) | 1
Benefits paid |  |  |  |  |  |  | (7 | ) |  | (6 | ) |  |  | (53 | ) |  | (46 | ) |
Benefit obligation at end of period |  |  |  |  |  |  | $ | 101 |  |  | $ | 112 |  |  |  | $ | 1,004 |  |  | $ | 1,053 |  |
Plan assets at fair value at beginning of period |  |  |  |  |  |  | $ | — |  |  | $ | — |  |  |  | $ | 1,329 |  |  | $ | 1,184 |  |
Actual return on plan assets |  |  |  |  |  |  | — |  |  | — |  |  |  | (80 | ) |  | 190 |  |
Company contribution |  |  |  |  |  |  | 7 |  |  | 6 |  |  |  | — |  |  | — |  |
Actual benefits paid |  |  |  |  |  |  | (7 | ) |  | (6 | ) |  |  | (52 | ) |  | (45 | ) |
Plan assets at fair value at end of period |  |  |  |  |  |  | $ | — |  |  | $ | — |  |  |  | $ | 1,197 |  |  | $ | 1,329 |  |
Funded status |  |  |  |  |  |  | $ | (101 | ) |  | $ | (112 | ) |  |  | $ | 193 |  |  | $ | 276 |  |
1 | The actuarial gain for 2018 for the DB Pension Plans was primarily the result of higher discount rates. The actuarial loss for 2017 was primarily the result of lower discount rates. The actuarial gain for 2018 for the OPEB Plan was primarily the result of higher discount rates. The actuarial gain for 2017 was primarily the result of better claim experience in calculating the plan’s funded status.
2 | At December 31, 2018, $246 million of the total funded status of the DB Pension Plans was attributable to Consumers, based on an allocation of expenses. At December 31, 2017, $455 million of the total funded status of the DB Pension Plans was attributable to Consumers, based on an allocation of expenses.
Schedule Of Retirement Benefit Plan Assets (Liabilities) | Presented in the following table is the classification of CMS Energy’s and Consumers’ retirement benefit plans’ assets and liabilities:
In Millions |
December 31 | 2018 |  | 2017 |
CMS Energy, including Consumers |  |  |  |
Non-current assets |  |  |  |
DB Pension Plans |  | $ | 38 |  |  | $ | 143 |
OPEB Plan |  | 235 |  |  | 323 |
Current liabilities |  |  |  |
DB SERP |  | 10 |  |  | 9 |
Non-current liabilities |  |  |  |  |  |
DB Pension Plans |  | 303 |  |  | 618 |
DB SERP |  | 130 |  |  | 145 |
Consumers |  |  |  |
Non-current assets |  |  |  |
DB Pension Plans |  | $ | 49 |  |  | $ | 147 |
OPEB Plan |  | 193 |  |  | 276 |
Current liabilities |  |  |  |
DB SERP |  | 7 |  |  | 7 |
Non-current liabilities |  |  |  |  |  |
DB Pension Plans |  | 295 |  |  | 602 |
DB SERP |  | 94 |  |  | 105 |
Schedule Of Net Periodic Benefit Cost Not Yet Recognized | For additional details on regulatory assets and liabilities, see Note 3, Regulatory Matters.
In Millions |
| DB Pension Plans and DB SERP |  | OPEB Plan
Years Ended December 31 | 2018 |  | 2017 |  |  | 2018 |  | 2017 |
CMS Energy, including Consumers |  |  |  |  |  |  |  |  |
Regulatory assets (liabilities) |  |  |  |  |  |  |  |  |
Net loss |  | $ | 978 |  |  | $ | 1,017 |  |  |  | $ | 402 |  |  | $ | 316 |
Prior service cost (credit) |  | 9 |  |  | 11 |  |  |  | (361 | ) |  | (451 | )
Regulatory assets (liabilities) |  | $ | 987 |  |  | $ | 1,028 |  |  |  | $ | 41 |  |  | $ | (135 | )
AOCI |  |  |  |  |  |  |  |  |
Net loss (gain) |  | 90 |  |  | 97 |  |  |  | 2 |  |  | (6 | )
Prior service cost (credit) |  | — |  |  | 1 |  |  |  | (9 | ) |  | (12 | )
Total amounts recognized in regulatory assets (liabilities) and AOCI |  | $ | 1,077 |  |  | $ | 1,126 |  |  |  | $ | 34 |  |  | $ | (153 | )
Consumers |  |  |  |  |  |  |  |  |
Regulatory assets (liabilities) |  |  |  |  |  |  |  |  |
Net loss |  | $ | 978 |  |  | $ | 1,017 |  |  |  | $ | 402 |  |  | $ | 316 |
Prior service cost (credit) |  | 9 |  |  | 11 |  |  |  | (361 | ) |  | (451 | )
Regulatory assets (liabilities) |  | $ | 987 |  |  | $ | 1,028 |  |  |  | $ | 41 |  |  | $ | (135 | )
AOCI |  |  |  |  |  |  |  |  |
Net loss |  | 27 |  |  | 36 |  |  |  | — |  |  | — |
Total amounts recognized in regulatory assets (liabilities) and AOCI |  | $ | 1,014 |  |  | $ | 1,064 |  |  |  | $ | 41 |  |  | $ | (135 | )
Schedule Of Plan Contributions | Presented in the following table are the contributions to CMS Energy’s and Consumers’ OPEB Plan and DB Pension Plans:
In Millions |
Years Ended December 31 | 2018 |  | 2017 |
CMS Energy, including Consumers |  |  |  |
OPEB Plan |  | $ | — |  |  | $ | — |
DB Pension Plans |  | 240 |  |  | — |
Consumers |  |  |  |
OPEB Plan |  | $ | — |  |  | $ | — |
DB Pension Plans |  | 234 |  |  | — |
Schedule Of Expected Benefit Payments | Presented in the following table are the expected benefit payments for each of the next five years and the five-year period thereafter:
In Millions |
| DB Pension Plans |  | DB SERP |  | OPEB Plan |
CMS Energy, including Consumers |  |  |  |  |  |
2019 |  | $ | 159 |  |  | $ | 10 |  |  | $ | 59 |
2020 |  | 162 |  |  | 10 |  |  | 61 |
2021 |  | 164 |  |  | 10 |  |  | 64 |
2022 |  | 165 |  |  | 10 |  |  | 65 |
2023 |  | 165 |  |  | 10 |  |  | 66 |
2024-2028 |  | 823 |  |  | 46 |  |  | 328 |
Consumers |  |  |  |  |  |
2019 |  | $ | 149 |  |  | $ | 7 |  |  | $ | 57 |
2020 |  | 152 |  |  | 7 |  |  | 59 |
2021 |  | 154 |  |  | 7 |  |  | 61 |
2022 |  | 155 |  |  | 7 |  |  | 62 |
2023 |  | 155 |  |  | 7 |  |  | 63 |
2024-2028 |  | 777 |  |  | 31 |  |  | 315 |

X
- Definition Schedule of Amounts in Accumulated Other Comprehensive Income (Loss) And Regulatory Assets (Liabilities) To Be Recognized Over Next Fiscal Year + References No definition available. + Details
Name: | cms_ScheduleOfAmountsInAccumulatedOtherComprehensiveIncomeLossAndRegulatoryAssetsLiabilitiesToBeRecognizedOverNextFiscalYearTableTextBlock
Namespace Prefix: | cms_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule Of Asset Allocation Percentages [Table Text Block] + References No definition available. + Details
Name: | cms_ScheduleOfAssetAllocationPercentagesTableTextBlock
Namespace Prefix: | cms_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule Of Net Periodic Benefit Cost Not Yet Recognized Including Regulatory Assets And Liabilities + References No definition available. + Details
Name: | cms_ScheduleOfNetPeriodicBenefitCostNotYetRecognizedIncludingRegulatoryAssetsAndLiabilitiesTableTextBlock
Namespace Prefix: | cms_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the DB SERP trust assets market value, amounts contributed to the DB SERP trust, and the ABO of the DB SERP. + References No definition available. + Details
Name: | cms_ScheduleofSERPtrustassetsABOandcontributionsTableTextBlockTableTextBlock
Namespace Prefix: | cms_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of plan contributions made. + References No definition available. + Details
Name: | cms_ScheduleofplancontributionsTableTextBlockTableTextBlock
Namespace Prefix: | cms_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the change in the benefit obligation, fair value of plan assets, and funded status of pension plans or other employee benefit plans. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(b)(c) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_ChangesInProjectedBenefitObligationsFairValueOfPlanAssetsAndFundedStatusOfPlanTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of benefit obligations including accumulated benefit obligation and projected benefit obligation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAccumulatedAndProjectedBenefitObligationsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAllocationOfPlanAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the amounts that are recognized in the balance sheet (or statement of financial position) for pension plans and/or other employee benefit plans, showing separately the assets and current and noncurrent liabilities (if applicable) recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAmountsRecognizedInBalanceSheetTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the assumptions used to determine for pension plans and/or other employee benefit plans the benefit obligation and net benefit cost, including assumed discount rates, rate increase in compensation increase, and expected long-term rates of return on plan assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAssumptionsUsedTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the effect of a one-percentage-point increase and the effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs and the accumulated postretirement benefit obligation for health care benefits. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfEffectOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of benefits expected to be paid by pension plans and/or other employee benefit plans in each of the next five fiscal years and in the aggregate for the five fiscal years thereafter. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfExpectedBenefitPaymentsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfNetBenefitCostsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=cms_ConsumersEnergyCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |