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Benefit Plans (Fair Value Of Plan Assets By Asset Category And Fair Value Hierarchy Level) (Details) - USD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | --- | ---
Pension Plans, Defined Benefit [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | $ 706.0 | $ 1,011.0 | $ 984.0
Assets measured at net asset value | 276.0 | 477.0 |
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 79.0 | 35.0 |
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 79.0 | 35.0 |
Pension Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 185.0 | 256.0 |
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 185.0 | 256.0 |
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | Global asset securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 35.0 | 52.0 |
Pension Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 35.0 | 52.0 |
Pension Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 130.0 | 191.0 |
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 30.0 | 47.0 |
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 100.0 | 144.0 |
Pension Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | Subtotal [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets in fair value hierarchy | 429.0 | 534.0 |
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 250.0 | 355.0 |
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 179.0 | 179.0 |
Pension Plans, Defined Benefit [Member] | Subtotal [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | Accrued investment income [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 1.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 344.0 | 462.0 | 453.0
Assets measured at net asset value | 124.0 | 218.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 62.0 | 16.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 62.0 | 16.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 83.0 | 117.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 83.0 | 117.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global asset securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 16.0 | 24.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global asset securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 16.0 | 24.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global asset securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Global asset securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 58.0 | 87.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 13.0 | 21.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 45.0 | 66.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets in fair value hierarchy | 219.0 | 244.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 112.0 | 162.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 107.0 | 82.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Subtotal [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | IPL [Member] | Accrued investment income [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 291.0 | 450.0 | 436.0
Assets measured at net asset value | 122.0 | 212.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 13.0 | 16.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 13.0 | 16.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 82.0 | 114.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 82.0 | 114.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global asset securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 16.0 | 23.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global asset securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 16.0 | 23.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global asset securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Global asset securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 57.0 | 85.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 13.0 | 21.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 44.0 | 64.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total assets in fair value hierarchy | 168.0 | 238.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 111.0 | 158.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 57.0 | 80.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Subtotal [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Pension Plans, Defined Benefit [Member] | WPL [Member] | Accrued investment income [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 83.0 | 106.0 | 108.0
Assets measured at net asset value | 23.0 | 29.0 |
Total assets in fair value hierarchy | 60.0 | 77.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 56.0 | 70.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 4.0 | 7.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 3.0 | 5.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 3.0 | 5.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Cash and equivalents [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 9.0 | 11.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 9.0 | 11.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Equity securites - U.S. [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global asset securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Global asset securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed income securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 47.0 | 60.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 46.0 | 58.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 2.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | Fixed income securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 58.0 | 74.0 | 74.0
Assets measured at net asset value | 18.0 | 23.0 |
Total assets in fair value hierarchy | 40.0 | 51.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 39.0 | 50.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Cash and equivalents [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 5.0 | 8.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 5.0 | 8.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Equity securites - U.S. [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 34.0 | 42.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 34.0 | 42.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | IPL [Member] | Fixed income securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 14.0 | 17.0 | $ 18.0
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 14.0 | 16.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Cash and equivalents [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 1.0 | 1.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Equity securites - U.S. [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 13.0 | 15.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 13.0 | 15.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Other Postretirement Benefit Plans, Defined Benefit [Member] | WPL [Member] | Fixed income securities [Member] | Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | 0.0 | 0.0 |
Defined Benefit Plan Due To Brokers Net [Member] | Pension Plans, Defined Benefit [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets | $ 0.0 | $ (1.0) |

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