Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Regulatory assets	$ 2,269	$ 2,046
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	919	929
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	371	392
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	282	70
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	199	151
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	138	160
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	72	84
IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	66
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	46	48
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	194	146
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,590	1,386
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	825	848
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	187	197
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	267	53
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	155	110
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	11	1
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	27	48
IPL [Member] | IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	48	66
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	70	63
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	679	660
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	94	81
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	184	195
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	15	17
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	44	41
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	127	159
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	45	36
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	46	48
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 124	$ 83