Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Regulatory assets	$ 1,940	$ 2,010
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	934	890
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	462	580
AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	128	119
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	92	113
IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	90	110
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	52	55
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	42	4
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	8	26
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	132	113
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,443	1,483
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	884	843
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	228	291
IPL [Member] | AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	89	81
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	66	77
IPL [Member] | IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	90	110
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	2	1
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	4	13
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	80	67
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	497	527
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	50	47
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	234	289
WPL [Member] | AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	39	38
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	26	36
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	52	55
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	40	3
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	4	13
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 52	$ 46