Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Regulatory Assets [Line Items]
Regulatory assets	$ 2,261	$ 2,046
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	934	929
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	347	392
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	273	70
AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	194	151
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	120	160
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	102	84
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	44	48
IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	42	66
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	205	146
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,577	1,386
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	831	848
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	171	197
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	259	53
IPL [Member] | AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	160	110
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	12	1
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	34	48
IPL [Member] | IPL's DAEC PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	42	66
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	68	63
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	684	660
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	103	81
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	176	195
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	14	17
WPL [Member] | AROs [Member]
Regulatory Assets [Line Items]
Regulatory assets	34	41
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	108	159
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	68	36
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	44	48
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 137	$ 83