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Benefit Plans (Narrative) (Details) $ in Millions | 3 Months Ended
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Mar. 31, 2021 USD ($) shares
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost | $ 13
Minimum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost recognized over a weighted average period | 1 year
Maximum [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost recognized over a weighted average period | 2 years
IPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost | $ 7
WPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Unrecognized compensation cost | $ 5
Omnibus Incentive Plan [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Shares included in diluted earnings per share (in shares) | shares | 425,849

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