Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Regulatory assets	$ 2,080	$ 2,046
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	942	929
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	385	392
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	156	151
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	152	160
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	101	84
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	67	70
IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	60	66
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	48
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	169	146
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,383	1,386
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	857	848
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	193	197
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	115	110
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	4	1
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	37	48
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	51	53
IPL [Member] | IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	60	66
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	66	63
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	697	660
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	85	81
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	192	195
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	41	41
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	148	159
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	64	36
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	16	17
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	48
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 103	$ 83