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Summary Of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2015
Schedule of Average Rates of Depreciation | The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:
| IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Electric - generation | 3.6% |  | 3.6% |  | 3.6% |  | 3.2% |  | 3.2% |  | 3.3%
Electric - distribution | 2.4% |  | 2.5% |  | 2.5% |  | 2.7% |  | 2.7% |  | 2.7%
Electric - other | 4.0% |  | 4.0% |  | 4.0% |  | 4.5% |  | 5.9% |  | 5.0%
Gas | 3.2% |  | 3.3% |  | 3.4% |  | 2.5% |  | 2.5% |  | 2.5%
Other | 3.9% |  | 4.3% |  | 4.7% |  | 6.0% |  | 6.0% |  | 5.1%
Schedule of Allowance for Funds Used During Construction Rate | The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows:
| 2015 |  | 2014 |  | 2013
IPL (Marshalltown CWIP) (a) | 7.9% |  | 8.0% |  | —%
IPL (other CWIP) | 7.7% |  | 7.8% |  | 8.2%
WPL (retail jurisdiction) | 8.2% |  | 8.2% |  | 8.2%
WPL (wholesale jurisdiction) | 7.9% |  | 4.1% |  | 4.5%
(a) | In 2013, the IUB issued an order establishing rate-making principles for Marshalltown that requires a 10.3% return on common equity for the calculation of AFUDC related to the construction of such facility.
Schedule of New Accounting Standards and Changes in Accounting Principles | The following financial statement line items were affected by these changes (in millions):
Alliant Energy | Originally |  | Effect of New |  | As
Balance Sheet as of December 31, 2014 | Reported |  | Accounting Standard |  | Adjusted
Deferred charges and other |  | $43.9 |  |  |  | ($22.4 | ) |  |  | $21.5 |
Total other assets | 1,759.5 |  |  | (22.4 | ) |  | 1,737.1 |
Total assets | 12,085.9 |  |  | (22.4 | ) |  | 12,063.5 |
Long-term debt, net (excluding current portion) | 3,606.7 |  |  | (22.4 | ) |  | 3,584.3 |
Total liabilities and equity | 12,085.9 |  |  | (22.4 | ) |  | 12,063.5 |
IPL | 2014 |  | 2013
Income Statements |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Income tax benefit |  | ($51.7 | ) |  |  | $2.8 |  |  |  | ($48.9 | ) |  |  | ($37.9 | ) |  |  | $1.6 |  |  |  | ($36.3 | )
Net income | 194.6 |  |  | (2.8 | ) |  | 191.8 |  |  | 189.9 |  |  | (1.6 | ) |  | 188.3 |
Earnings available for common stock | 184.4 |  |  | (2.8 | ) |  | 181.6 |  |  | 173.6 |  |  | (1.6 | ) |  | 172.0 |
IPL |  |  | Effect of New |  | Effect of Change in |  |
Balance Sheets | Originally |  | Accounting |  | Method of Calculating |  | As
December 31, 2014 | Reported |  | Standard |  | Income Taxes |  | Adjusted
Deferred tax assets |  | $104.9 |  |  |  | $— |  |  |  | ($0.9 | ) |  |  | $104.0 |
Total current assets | 556.1 |  |  | — |  |  | (0.9 | ) |  | 555.2 |
Deferred charges and other | 12.7 |  |  | (10.7 | ) |  | — |  |  | 2.0 |
Total other assets | 1,331.9 |  |  | (10.7 | ) |  | — |  |  | 1,321.2 |
Total assets | 6,461.8 |  |  | (10.7 | ) |  | (0.9 | ) |  | 6,450.2 |
Long-term debt, net (excluding current portion) | 1,618.7 |  |  | (10.7 | ) |  | — |  |  | 1,608.0 |
Deferred tax liabilities | 1,341.4 |  |  | — |  |  | 28.9 |  |  | 1,370.3 |
Total other liabilities | 2,123.1 |  |  | — |  |  | 28.9 |  |  | 2,152.0 |
Retained earnings | 537.9 |  |  | — |  |  | (29.8 | ) |  | 508.1 |
Total IPL common equity | 1,814.1 |  |  | — |  |  | (29.8 | ) |  | 1,784.3 |
Total equity | 2,014.1 |  |  | — |  |  | (29.8 | ) |  | 1,984.3 |
Total liabilities and equity | 6,461.8 |  |  | (10.7 | ) |  | (0.9 | ) |  | 6,450.2 |
January 1, 2014 |  |  |  |  |  |  |
Retained earnings | 493.5 |  |  | — |  |  | (31.6 | ) |  | 461.9 |
January 1, 2013 |  |  |  |  |  |  |
Retained earnings | 448.0 |  |  | — |  |  | (32.8 | ) |  | 415.2 |
IPL | 2014 |  | 2013
Cash Flows |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Net income |  | $194.6 |  |  |  | ($2.8 | ) |  |  | $191.8 |  |  |  | $189.9 |  |  |  | ($1.6 | ) |  |  | $188.3 |
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Deferred tax expense (benefit) and investment tax credits | (9.7 | ) |  | (1.8 | ) |  | (11.5 | ) |  | 4.2 |  |  | (1.2 | ) |  | 3.0 |
Other changes in assets and liabilities: |  |  |  |  |  |  |  |  |  |  |
Other | 32.0 |  |  | 4.6 |  |  | 36.6 |  |  | (14.0 | ) |  | 2.8 |  |  | (11.2 | )
WPL | 2014 |  | 2013
Income Statements |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Income taxes |  | $85.6 |  |  |  | ($0.3 | ) |  |  | $85.3 |  |  |  | $87.2 |  |  |  | ($1.6 | ) |  |  | $85.6 |
Net income | 180.8 |  |  | 0.3 |  |  | 181.1 |  |  | 177.5 |  |  | 1.6 |  |  | 179.1 |
Earnings available for common stock | 180.1 |  |  | 0.3 |  |  | 180.4 |  |  | 175.9 |  |  | 1.6 |  |  | 177.5 |
WPL |  |  | Effect of New |  | Effect of Change in |  |
Balance Sheets | Originally |  | Accounting |  | Method of Calculating |  | As
December 31, 2014 | Reported |  | Standard |  | Income Taxes |  | Adjusted
Deferred tax assets |  | $37.5 |  |  |  | $— |  |  |  | $0.2 |  |  |  | $37.7 |
Total current assets | 457.2 |  |  | — |  |  | 0.2 |  |  | 457.4 |
Deferred charges and other | 29.7 |  |  | (10.8 | ) |  | — |  |  | 18.9 |
Total other assets | 426.1 |  |  | (10.8 | ) |  | — |  |  | 415.3 |
Total assets | 5,128.2 |  |  | (10.8 | ) |  | 0.2 |  |  | 5,117.6 |
Long-term debt, net (excluding current portion) | 1,543.3 |  |  | (10.8 | ) |  | — |  |  | 1,532.5 |
Deferred tax liabilities | 970.0 |  |  | — |  |  | (2.9 | ) |  | 967.1 |
Total other liabilities | 1,562.3 |  |  | — |  |  | (2.9 | ) |  | 1,559.4 |
Retained earnings | 678.6 |  |  | — |  |  | 3.1 |  |  | 681.7 |
Total WPL common equity | 1,703.8 |  |  | — |  |  | 3.1 |  |  | 1,706.9 |
Total equity | 1,712.3 |  |  | — |  |  | 3.1 |  |  | 1,715.4 |
Total liabilities and equity | 5,128.2 |  |  | (10.8 | ) |  | 0.2 |  |  | 5,117.6 |
January 1, 2014 |  |  |  |  |  |  |
Retained earnings | 617.2 |  |  | — |  |  | 5.0 |  |  | 622.2 |
January 1, 2013 |  |  |  |  |  |  |
Retained earnings | 557.6 |  |  | — |  |  | 8.3 |  |  | 565.9 |
WPL | 2014 |  | 2013
Cash Flows |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Net income |  | $180.8 |  |  |  | $0.3 |  |  |  | $181.1 |  |  |  | $177.5 |  |  |  | $1.6 |  |  |  | $179.1 |
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Deferred tax expense and investment tax credits | 80.7 |  |  | 1.9 |  |  | 82.6 |  |  | 86.5 |  |  | 3.3 |  |  | 89.8 |
Other changes in assets and liabilities: |  |  |  |  |  |  |  |  |  |  |
Other | (6.8 | ) |  | (2.2 | ) |  | (9.0 | ) |  | (16.7 | ) |  | (4.9 | ) |  | (21.6 | )
The change in method of calculating the income tax provisions and related deferred tax assets and liabilities for IPL and WPL did not have a material impact on their income statements or cash flows statements for 2015. The following balance sheet line items for 2015 were affected by this change in method for IPL and WPL (in millions):
IPL | As Computed Under |  | As Reported Under |  |
Balance Sheet as of December 31, 2015 | Parent-company-down |  | Modified Separate |  | Effect of
| Approach |  | Return Approach |  | Change
Deferred tax liabilities |  | $1,346.7 |  |  |  | $1,378.0 |  |  |  | $31.3 |
Total other liabilities | 2,094.5 |  |  | 2,125.8 |  |  | 31.3 |
Retained earnings | 585.4 |  |  | 554.1 |  |  | (31.3 | )
Total IPL common equity | 2,026.6 |  |  | 1,995.3 |  |  | (31.3 | )
Total equity | 2,226.6 |  |  | 2,195.3 |  |  | (31.3 | )
WPL | As Computed Under |  | As Reported Under |  |
Balance Sheet as of December 31, 2015 | Parent-company-down |  | Modified Separate |  | Effect of
| Approach |  | Return Approach |  | Change
Other current liabilities |  | $78.2 |  |  |  | $79.5 |  |  |  | $1.3 |
Total current liabilities | 335.6 |  |  | 336.9 |  |  | 1.3 |
Deferred tax liabilities | 1,010.8 |  |  | 1,005.4 |  |  | (5.4 | )
Total other liabilities | 1,637.4 |  |  | 1,632.0 |  |  | (5.4 | )
Retained earnings | 727.0 |  |  | 731.1 |  |  | 4.1 |
Total WPL common equity | 1,752.2 |  |  | 1,756.3 |  |  | 4.1 |
Total equity | 1,763.5 |  |  | 1,767.6 |  |  | 4.1 |
In addition, the following previously reported Selected Consolidated Quarterly Financial Data (Unaudited) for the three months ended were impacted as a result of the change in method of calculating the income tax provisions and related deferred tax assets and liabilities for IPL and WPL (in millions):
| March 31, 2015 |  | June 30, 2015 |  | September 30, 2015
| Originally |  | As |  | Originally |  | As |  | Originally |  | As
| Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted
IPL |  |  |  |  |  |  |  |  |  |  |
Net income |  | $50.4 |  |  |  | $50.1 |  |  |  | $19.2 |  |  |  | $19.0 |  |  |  | $120.0 |  |  |  | $119.1 |
Earnings available for common stock | 47.8 |  |  | 47.5 |  |  | 16.7 |  |  | 16.5 |  |  | 117.4 |  |  | 116.5 |
WPL |  |  |  |  |  |  |  |  |  |  |
Net income | 44.8 |  |  | 45.1 |  |  | 39.5 |  |  | 39.7 |  |  | 67.9 |  |  | 68.4 |
Earnings available for common stock | 44.6 |  |  | 44.9 |  |  | 39.0 |  |  | 39.2 |  |  | 67.5 |  |  | 68.0 |
| March 31, 2014 |  | June 30, 2014 |  | September 30, 2014 |  | December 31, 2014
| Originally |  | As |  | Originally |  | As |  | Originally |  | As |  | Originally |  | As
| Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted
IPL |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net income |  | $46.0 |  |  |  | $45.3 |  |  |  | $20.9 |  |  |  | $20.5 |  |  |  | $105.1 |  |  |  | $104.6 |  |  |  | $22.6 |  |  |  | $21.4 |
Earnings available for common stock | 43.4 |  |  | 42.7 |  |  | 18.4 |  |  | 18.0 |  |  | 102.5 |  |  | 102.0 |  |  | 20.1 |  |  | 18.9 |
WPL |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net income | 54.8 |  |  | 55.2 |  |  | 34.6 |  |  | 34.7 |  |  | 61.6 |  |  | 57.9 |  |  | 29.8 |  |  | 33.3 |
Earnings available for common stock | 54.8 |  |  | 55.2 |  |  | 34.6 |  |  | 34.7 |  |  | 61.6 |  |  | 57.9 |  |  | 29.1 |  |  | 32.6 |
IPL [Member] |
Schedule of Average Rates of Depreciation | The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:
| IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Electric - generation | 3.6% |  | 3.6% |  | 3.6% |  | 3.2% |  | 3.2% |  | 3.3%
Electric - distribution | 2.4% |  | 2.5% |  | 2.5% |  | 2.7% |  | 2.7% |  | 2.7%
Electric - other | 4.0% |  | 4.0% |  | 4.0% |  | 4.5% |  | 5.9% |  | 5.0%
Gas | 3.2% |  | 3.3% |  | 3.4% |  | 2.5% |  | 2.5% |  | 2.5%
Other | 3.9% |  | 4.3% |  | 4.7% |  | 6.0% |  | 6.0% |  | 5.1%
Schedule of Allowance for Funds Used During Construction Rate | The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows:
| 2015 |  | 2014 |  | 2013
IPL (Marshalltown CWIP) (a) | 7.9% |  | 8.0% |  | —%
IPL (other CWIP) | 7.7% |  | 7.8% |  | 8.2%
WPL (retail jurisdiction) | 8.2% |  | 8.2% |  | 8.2%
WPL (wholesale jurisdiction) | 7.9% |  | 4.1% |  | 4.5%
(a) | In 2013, the IUB issued an order establishing rate-making principles for Marshalltown that requires a 10.3% return on common equity for the calculation of AFUDC related to the construction of such facility.
Schedule of New Accounting Standards and Changes in Accounting Principles | The following financial statement line items were affected by these changes (in millions):
Alliant Energy | Originally |  | Effect of New |  | As
Balance Sheet as of December 31, 2014 | Reported |  | Accounting Standard |  | Adjusted
Deferred charges and other |  | $43.9 |  |  |  | ($22.4 | ) |  |  | $21.5 |
Total other assets | 1,759.5 |  |  | (22.4 | ) |  | 1,737.1 |
Total assets | 12,085.9 |  |  | (22.4 | ) |  | 12,063.5 |
Long-term debt, net (excluding current portion) | 3,606.7 |  |  | (22.4 | ) |  | 3,584.3 |
Total liabilities and equity | 12,085.9 |  |  | (22.4 | ) |  | 12,063.5 |
IPL | 2014 |  | 2013
Income Statements |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Income tax benefit |  | ($51.7 | ) |  |  | $2.8 |  |  |  | ($48.9 | ) |  |  | ($37.9 | ) |  |  | $1.6 |  |  |  | ($36.3 | )
Net income | 194.6 |  |  | (2.8 | ) |  | 191.8 |  |  | 189.9 |  |  | (1.6 | ) |  | 188.3 |
Earnings available for common stock | 184.4 |  |  | (2.8 | ) |  | 181.6 |  |  | 173.6 |  |  | (1.6 | ) |  | 172.0 |
IPL |  |  | Effect of New |  | Effect of Change in |  |
Balance Sheets | Originally |  | Accounting |  | Method of Calculating |  | As
December 31, 2014 | Reported |  | Standard |  | Income Taxes |  | Adjusted
Deferred tax assets |  | $104.9 |  |  |  | $— |  |  |  | ($0.9 | ) |  |  | $104.0 |
Total current assets | 556.1 |  |  | — |  |  | (0.9 | ) |  | 555.2 |
Deferred charges and other | 12.7 |  |  | (10.7 | ) |  | — |  |  | 2.0 |
Total other assets | 1,331.9 |  |  | (10.7 | ) |  | — |  |  | 1,321.2 |
Total assets | 6,461.8 |  |  | (10.7 | ) |  | (0.9 | ) |  | 6,450.2 |
Long-term debt, net (excluding current portion) | 1,618.7 |  |  | (10.7 | ) |  | — |  |  | 1,608.0 |
Deferred tax liabilities | 1,341.4 |  |  | — |  |  | 28.9 |  |  | 1,370.3 |
Total other liabilities | 2,123.1 |  |  | — |  |  | 28.9 |  |  | 2,152.0 |
Retained earnings | 537.9 |  |  | — |  |  | (29.8 | ) |  | 508.1 |
Total IPL common equity | 1,814.1 |  |  | — |  |  | (29.8 | ) |  | 1,784.3 |
Total equity | 2,014.1 |  |  | — |  |  | (29.8 | ) |  | 1,984.3 |
Total liabilities and equity | 6,461.8 |  |  | (10.7 | ) |  | (0.9 | ) |  | 6,450.2 |
January 1, 2014 |  |  |  |  |  |  |
Retained earnings | 493.5 |  |  | — |  |  | (31.6 | ) |  | 461.9 |
January 1, 2013 |  |  |  |  |  |  |
Retained earnings | 448.0 |  |  | — |  |  | (32.8 | ) |  | 415.2 |
IPL | 2014 |  | 2013
Cash Flows |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Net income |  | $194.6 |  |  |  | ($2.8 | ) |  |  | $191.8 |  |  |  | $189.9 |  |  |  | ($1.6 | ) |  |  | $188.3 |
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Deferred tax expense (benefit) and investment tax credits | (9.7 | ) |  | (1.8 | ) |  | (11.5 | ) |  | 4.2 |  |  | (1.2 | ) |  | 3.0 |
Other changes in assets and liabilities: |  |  |  |  |  |  |  |  |  |  |
Other | 32.0 |  |  | 4.6 |  |  | 36.6 |  |  | (14.0 | ) |  | 2.8 |  |  | (11.2 | )
WPL | 2014 |  | 2013
Income Statements |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Income taxes |  | $85.6 |  |  |  | ($0.3 | ) |  |  | $85.3 |  |  |  | $87.2 |  |  |  | ($1.6 | ) |  |  | $85.6 |
Net income | 180.8 |  |  | 0.3 |  |  | 181.1 |  |  | 177.5 |  |  | 1.6 |  |  | 179.1 |
Earnings available for common stock | 180.1 |  |  | 0.3 |  |  | 180.4 |  |  | 175.9 |  |  | 1.6 |  |  | 177.5 |
WPL |  |  | Effect of New |  | Effect of Change in |  |
Balance Sheets | Originally |  | Accounting |  | Method of Calculating |  | As
December 31, 2014 | Reported |  | Standard |  | Income Taxes |  | Adjusted
Deferred tax assets |  | $37.5 |  |  |  | $— |  |  |  | $0.2 |  |  |  | $37.7 |
Total current assets | 457.2 |  |  | — |  |  | 0.2 |  |  | 457.4 |
Deferred charges and other | 29.7 |  |  | (10.8 | ) |  | — |  |  | 18.9 |
Total other assets | 426.1 |  |  | (10.8 | ) |  | — |  |  | 415.3 |
Total assets | 5,128.2 |  |  | (10.8 | ) |  | 0.2 |  |  | 5,117.6 |
Long-term debt, net (excluding current portion) | 1,543.3 |  |  | (10.8 | ) |  | — |  |  | 1,532.5 |
Deferred tax liabilities | 970.0 |  |  | — |  |  | (2.9 | ) |  | 967.1 |
Total other liabilities | 1,562.3 |  |  | — |  |  | (2.9 | ) |  | 1,559.4 |
Retained earnings | 678.6 |  |  | — |  |  | 3.1 |  |  | 681.7 |
Total WPL common equity | 1,703.8 |  |  | — |  |  | 3.1 |  |  | 1,706.9 |
Total equity | 1,712.3 |  |  | — |  |  | 3.1 |  |  | 1,715.4 |
Total liabilities and equity | 5,128.2 |  |  | (10.8 | ) |  | 0.2 |  |  | 5,117.6 |
January 1, 2014 |  |  |  |  |  |  |
Retained earnings | 617.2 |  |  | — |  |  | 5.0 |  |  | 622.2 |
January 1, 2013 |  |  |  |  |  |  |
Retained earnings | 557.6 |  |  | — |  |  | 8.3 |  |  | 565.9 |
WPL | 2014 |  | 2013
Cash Flows |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Net income |  | $180.8 |  |  |  | $0.3 |  |  |  | $181.1 |  |  |  | $177.5 |  |  |  | $1.6 |  |  |  | $179.1 |
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Deferred tax expense and investment tax credits | 80.7 |  |  | 1.9 |  |  | 82.6 |  |  | 86.5 |  |  | 3.3 |  |  | 89.8 |
Other changes in assets and liabilities: |  |  |  |  |  |  |  |  |  |  |
Other | (6.8 | ) |  | (2.2 | ) |  | (9.0 | ) |  | (16.7 | ) |  | (4.9 | ) |  | (21.6 | )
The change in method of calculating the income tax provisions and related deferred tax assets and liabilities for IPL and WPL did not have a material impact on their income statements or cash flows statements for 2015. The following balance sheet line items for 2015 were affected by this change in method for IPL and WPL (in millions):
IPL | As Computed Under |  | As Reported Under |  |
Balance Sheet as of December 31, 2015 | Parent-company-down |  | Modified Separate |  | Effect of
| Approach |  | Return Approach |  | Change
Deferred tax liabilities |  | $1,346.7 |  |  |  | $1,378.0 |  |  |  | $31.3 |
Total other liabilities | 2,094.5 |  |  | 2,125.8 |  |  | 31.3 |
Retained earnings | 585.4 |  |  | 554.1 |  |  | (31.3 | )
Total IPL common equity | 2,026.6 |  |  | 1,995.3 |  |  | (31.3 | )
Total equity | 2,226.6 |  |  | 2,195.3 |  |  | (31.3 | )
WPL | As Computed Under |  | As Reported Under |  |
Balance Sheet as of December 31, 2015 | Parent-company-down |  | Modified Separate |  | Effect of
| Approach |  | Return Approach |  | Change
Other current liabilities |  | $78.2 |  |  |  | $79.5 |  |  |  | $1.3 |
Total current liabilities | 335.6 |  |  | 336.9 |  |  | 1.3 |
Deferred tax liabilities | 1,010.8 |  |  | 1,005.4 |  |  | (5.4 | )
Total other liabilities | 1,637.4 |  |  | 1,632.0 |  |  | (5.4 | )
Retained earnings | 727.0 |  |  | 731.1 |  |  | 4.1 |
Total WPL common equity | 1,752.2 |  |  | 1,756.3 |  |  | 4.1 |
Total equity | 1,763.5 |  |  | 1,767.6 |  |  | 4.1 |
In addition, the following previously reported Selected Consolidated Quarterly Financial Data (Unaudited) for the three months ended were impacted as a result of the change in method of calculating the income tax provisions and related deferred tax assets and liabilities for IPL and WPL (in millions):
| March 31, 2015 |  | June 30, 2015 |  | September 30, 2015
| Originally |  | As |  | Originally |  | As |  | Originally |  | As
| Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted
IPL |  |  |  |  |  |  |  |  |  |  |
Net income |  | $50.4 |  |  |  | $50.1 |  |  |  | $19.2 |  |  |  | $19.0 |  |  |  | $120.0 |  |  |  | $119.1 |
Earnings available for common stock | 47.8 |  |  | 47.5 |  |  | 16.7 |  |  | 16.5 |  |  | 117.4 |  |  | 116.5 |
WPL |  |  |  |  |  |  |  |  |  |  |
Net income | 44.8 |  |  | 45.1 |  |  | 39.5 |  |  | 39.7 |  |  | 67.9 |  |  | 68.4 |
Earnings available for common stock | 44.6 |  |  | 44.9 |  |  | 39.0 |  |  | 39.2 |  |  | 67.5 |  |  | 68.0 |
| March 31, 2014 |  | June 30, 2014 |  | September 30, 2014 |  | December 31, 2014
| Originally |  | As |  | Originally |  | As |  | Originally |  | As |  | Originally |  | As
| Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted
IPL |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net income |  | $46.0 |  |  |  | $45.3 |  |  |  | $20.9 |  |  |  | $20.5 |  |  |  | $105.1 |  |  |  | $104.6 |  |  |  | $22.6 |  |  |  | $21.4 |
Earnings available for common stock | 43.4 |  |  | 42.7 |  |  | 18.4 |  |  | 18.0 |  |  | 102.5 |  |  | 102.0 |  |  | 20.1 |  |  | 18.9 |
WPL |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net income | 54.8 |  |  | 55.2 |  |  | 34.6 |  |  | 34.7 |  |  | 61.6 |  |  | 57.9 |  |  | 29.8 |  |  | 33.3 |
Earnings available for common stock | 54.8 |  |  | 55.2 |  |  | 34.6 |  |  | 34.7 |  |  | 61.6 |  |  | 57.9 |  |  | 29.1 |  |  | 32.6 |
WPL [Member] |
Schedule of Average Rates of Depreciation | The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:
| IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Electric - generation | 3.6% |  | 3.6% |  | 3.6% |  | 3.2% |  | 3.2% |  | 3.3%
Electric - distribution | 2.4% |  | 2.5% |  | 2.5% |  | 2.7% |  | 2.7% |  | 2.7%
Electric - other | 4.0% |  | 4.0% |  | 4.0% |  | 4.5% |  | 5.9% |  | 5.0%
Gas | 3.2% |  | 3.3% |  | 3.4% |  | 2.5% |  | 2.5% |  | 2.5%
Other | 3.9% |  | 4.3% |  | 4.7% |  | 6.0% |  | 6.0% |  | 5.1%
Schedule of Allowance for Funds Used During Construction Rate | The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows:
| 2015 |  | 2014 |  | 2013
IPL (Marshalltown CWIP) (a) | 7.9% |  | 8.0% |  | —%
IPL (other CWIP) | 7.7% |  | 7.8% |  | 8.2%
WPL (retail jurisdiction) | 8.2% |  | 8.2% |  | 8.2%
WPL (wholesale jurisdiction) | 7.9% |  | 4.1% |  | 4.5%
(a) | In 2013, the IUB issued an order establishing rate-making principles for Marshalltown that requires a 10.3% return on common equity for the calculation of AFUDC related to the construction of such facility.
Schedule of New Accounting Standards and Changes in Accounting Principles | The following financial statement line items were affected by these changes (in millions):
Alliant Energy | Originally |  | Effect of New |  | As
Balance Sheet as of December 31, 2014 | Reported |  | Accounting Standard |  | Adjusted
Deferred charges and other |  | $43.9 |  |  |  | ($22.4 | ) |  |  | $21.5 |
Total other assets | 1,759.5 |  |  | (22.4 | ) |  | 1,737.1 |
Total assets | 12,085.9 |  |  | (22.4 | ) |  | 12,063.5 |
Long-term debt, net (excluding current portion) | 3,606.7 |  |  | (22.4 | ) |  | 3,584.3 |
Total liabilities and equity | 12,085.9 |  |  | (22.4 | ) |  | 12,063.5 |
IPL | 2014 |  | 2013
Income Statements |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Income tax benefit |  | ($51.7 | ) |  |  | $2.8 |  |  |  | ($48.9 | ) |  |  | ($37.9 | ) |  |  | $1.6 |  |  |  | ($36.3 | )
Net income | 194.6 |  |  | (2.8 | ) |  | 191.8 |  |  | 189.9 |  |  | (1.6 | ) |  | 188.3 |
Earnings available for common stock | 184.4 |  |  | (2.8 | ) |  | 181.6 |  |  | 173.6 |  |  | (1.6 | ) |  | 172.0 |
IPL |  |  | Effect of New |  | Effect of Change in |  |
Balance Sheets | Originally |  | Accounting |  | Method of Calculating |  | As
December 31, 2014 | Reported |  | Standard |  | Income Taxes |  | Adjusted
Deferred tax assets |  | $104.9 |  |  |  | $— |  |  |  | ($0.9 | ) |  |  | $104.0 |
Total current assets | 556.1 |  |  | — |  |  | (0.9 | ) |  | 555.2 |
Deferred charges and other | 12.7 |  |  | (10.7 | ) |  | — |  |  | 2.0 |
Total other assets | 1,331.9 |  |  | (10.7 | ) |  | — |  |  | 1,321.2 |
Total assets | 6,461.8 |  |  | (10.7 | ) |  | (0.9 | ) |  | 6,450.2 |
Long-term debt, net (excluding current portion) | 1,618.7 |  |  | (10.7 | ) |  | — |  |  | 1,608.0 |
Deferred tax liabilities | 1,341.4 |  |  | — |  |  | 28.9 |  |  | 1,370.3 |
Total other liabilities | 2,123.1 |  |  | — |  |  | 28.9 |  |  | 2,152.0 |
Retained earnings | 537.9 |  |  | — |  |  | (29.8 | ) |  | 508.1 |
Total IPL common equity | 1,814.1 |  |  | — |  |  | (29.8 | ) |  | 1,784.3 |
Total equity | 2,014.1 |  |  | — |  |  | (29.8 | ) |  | 1,984.3 |
Total liabilities and equity | 6,461.8 |  |  | (10.7 | ) |  | (0.9 | ) |  | 6,450.2 |
January 1, 2014 |  |  |  |  |  |  |
Retained earnings | 493.5 |  |  | — |  |  | (31.6 | ) |  | 461.9 |
January 1, 2013 |  |  |  |  |  |  |
Retained earnings | 448.0 |  |  | — |  |  | (32.8 | ) |  | 415.2 |
IPL | 2014 |  | 2013
Cash Flows |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Net income |  | $194.6 |  |  |  | ($2.8 | ) |  |  | $191.8 |  |  |  | $189.9 |  |  |  | ($1.6 | ) |  |  | $188.3 |
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Deferred tax expense (benefit) and investment tax credits | (9.7 | ) |  | (1.8 | ) |  | (11.5 | ) |  | 4.2 |  |  | (1.2 | ) |  | 3.0 |
Other changes in assets and liabilities: |  |  |  |  |  |  |  |  |  |  |
Other | 32.0 |  |  | 4.6 |  |  | 36.6 |  |  | (14.0 | ) |  | 2.8 |  |  | (11.2 | )
WPL | 2014 |  | 2013
Income Statements |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Income taxes |  | $85.6 |  |  |  | ($0.3 | ) |  |  | $85.3 |  |  |  | $87.2 |  |  |  | ($1.6 | ) |  |  | $85.6 |
Net income | 180.8 |  |  | 0.3 |  |  | 181.1 |  |  | 177.5 |  |  | 1.6 |  |  | 179.1 |
Earnings available for common stock | 180.1 |  |  | 0.3 |  |  | 180.4 |  |  | 175.9 |  |  | 1.6 |  |  | 177.5 |
WPL |  |  | Effect of New |  | Effect of Change in |  |
Balance Sheets | Originally |  | Accounting |  | Method of Calculating |  | As
December 31, 2014 | Reported |  | Standard |  | Income Taxes |  | Adjusted
Deferred tax assets |  | $37.5 |  |  |  | $— |  |  |  | $0.2 |  |  |  | $37.7 |
Total current assets | 457.2 |  |  | — |  |  | 0.2 |  |  | 457.4 |
Deferred charges and other | 29.7 |  |  | (10.8 | ) |  | — |  |  | 18.9 |
Total other assets | 426.1 |  |  | (10.8 | ) |  | — |  |  | 415.3 |
Total assets | 5,128.2 |  |  | (10.8 | ) |  | 0.2 |  |  | 5,117.6 |
Long-term debt, net (excluding current portion) | 1,543.3 |  |  | (10.8 | ) |  | — |  |  | 1,532.5 |
Deferred tax liabilities | 970.0 |  |  | — |  |  | (2.9 | ) |  | 967.1 |
Total other liabilities | 1,562.3 |  |  | — |  |  | (2.9 | ) |  | 1,559.4 |
Retained earnings | 678.6 |  |  | — |  |  | 3.1 |  |  | 681.7 |
Total WPL common equity | 1,703.8 |  |  | — |  |  | 3.1 |  |  | 1,706.9 |
Total equity | 1,712.3 |  |  | — |  |  | 3.1 |  |  | 1,715.4 |
Total liabilities and equity | 5,128.2 |  |  | (10.8 | ) |  | 0.2 |  |  | 5,117.6 |
January 1, 2014 |  |  |  |  |  |  |
Retained earnings | 617.2 |  |  | — |  |  | 5.0 |  |  | 622.2 |
January 1, 2013 |  |  |  |  |  |  |
Retained earnings | 557.6 |  |  | — |  |  | 8.3 |  |  | 565.9 |
WPL | 2014 |  | 2013
Cash Flows |  |  | Effect of Change in |  |  |  |  |  | Effect of Change in |  |
| Originally |  | Method of Calculating |  | As |  | Originally |  | Method of Calculating |  | As
| Reported |  | Income Taxes |  | Adjusted |  | Reported |  | Income Taxes |  | Adjusted
Cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Net income |  | $180.8 |  |  |  | $0.3 |  |  |  | $181.1 |  |  |  | $177.5 |  |  |  | $1.6 |  |  |  | $179.1 |
Adjustments to reconcile net income to net cash flows from operating activities: |  |  |  |  |  |  |  |  |  |  |
Deferred tax expense and investment tax credits | 80.7 |  |  | 1.9 |  |  | 82.6 |  |  | 86.5 |  |  | 3.3 |  |  | 89.8 |
Other changes in assets and liabilities: |  |  |  |  |  |  |  |  |  |  |
Other | (6.8 | ) |  | (2.2 | ) |  | (9.0 | ) |  | (16.7 | ) |  | (4.9 | ) |  | (21.6 | )
The change in method of calculating the income tax provisions and related deferred tax assets and liabilities for IPL and WPL did not have a material impact on their income statements or cash flows statements for 2015. The following balance sheet line items for 2015 were affected by this change in method for IPL and WPL (in millions):
IPL | As Computed Under |  | As Reported Under |  |
Balance Sheet as of December 31, 2015 | Parent-company-down |  | Modified Separate |  | Effect of
| Approach |  | Return Approach |  | Change
Deferred tax liabilities |  | $1,346.7 |  |  |  | $1,378.0 |  |  |  | $31.3 |
Total other liabilities | 2,094.5 |  |  | 2,125.8 |  |  | 31.3 |
Retained earnings | 585.4 |  |  | 554.1 |  |  | (31.3 | )
Total IPL common equity | 2,026.6 |  |  | 1,995.3 |  |  | (31.3 | )
Total equity | 2,226.6 |  |  | 2,195.3 |  |  | (31.3 | )
WPL | As Computed Under |  | As Reported Under |  |
Balance Sheet as of December 31, 2015 | Parent-company-down |  | Modified Separate |  | Effect of
| Approach |  | Return Approach |  | Change
Other current liabilities |  | $78.2 |  |  |  | $79.5 |  |  |  | $1.3 |
Total current liabilities | 335.6 |  |  | 336.9 |  |  | 1.3 |
Deferred tax liabilities | 1,010.8 |  |  | 1,005.4 |  |  | (5.4 | )
Total other liabilities | 1,637.4 |  |  | 1,632.0 |  |  | (5.4 | )
Retained earnings | 727.0 |  |  | 731.1 |  |  | 4.1 |
Total WPL common equity | 1,752.2 |  |  | 1,756.3 |  |  | 4.1 |
Total equity | 1,763.5 |  |  | 1,767.6 |  |  | 4.1 |
In addition, the following previously reported Selected Consolidated Quarterly Financial Data (Unaudited) for the three months ended were impacted as a result of the change in method of calculating the income tax provisions and related deferred tax assets and liabilities for IPL and WPL (in millions):
| March 31, 2015 |  | June 30, 2015 |  | September 30, 2015
| Originally |  | As |  | Originally |  | As |  | Originally |  | As
| Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted
IPL |  |  |  |  |  |  |  |  |  |  |
Net income |  | $50.4 |  |  |  | $50.1 |  |  |  | $19.2 |  |  |  | $19.0 |  |  |  | $120.0 |  |  |  | $119.1 |
Earnings available for common stock | 47.8 |  |  | 47.5 |  |  | 16.7 |  |  | 16.5 |  |  | 117.4 |  |  | 116.5 |
WPL |  |  |  |  |  |  |  |  |  |  |
Net income | 44.8 |  |  | 45.1 |  |  | 39.5 |  |  | 39.7 |  |  | 67.9 |  |  | 68.4 |
Earnings available for common stock | 44.6 |  |  | 44.9 |  |  | 39.0 |  |  | 39.2 |  |  | 67.5 |  |  | 68.0 |
| March 31, 2014 |  | June 30, 2014 |  | September 30, 2014 |  | December 31, 2014
| Originally |  | As |  | Originally |  | As |  | Originally |  | As |  | Originally |  | As
| Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted |  | Reported |  | Adjusted
IPL |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net income |  | $46.0 |  |  |  | $45.3 |  |  |  | $20.9 |  |  |  | $20.5 |  |  |  | $105.1 |  |  |  | $104.6 |  |  |  | $22.6 |  |  |  | $21.4 |
Earnings available for common stock | 43.4 |  |  | 42.7 |  |  | 18.4 |  |  | 18.0 |  |  | 102.5 |  |  | 102.0 |  |  | 20.1 |  |  | 18.9 |
WPL |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net income | 54.8 |  |  | 55.2 |  |  | 34.6 |  |  | 34.7 |  |  | 61.6 |  |  | 57.9 |  |  | 29.8 |  |  | 33.3 |
Earnings available for common stock | 54.8 |  |  | 55.2 |  |  | 34.6 |  |  | 34.7 |  |  | 61.6 |  |  | 57.9 |  |  | 29.1 |  |  | 32.6 |

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