Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Regulatory Assets [Line Items]
Regulatory assets	$ 2,220	$ 2,261
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	939	934
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	340	347
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	267	273
Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	200	194
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	100	120
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	97	102
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	44	44
IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	36	42
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	197	205
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,567	1,577
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	839	831
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	168	171
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	253	259
IPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	165	160
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	5	12
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	33	34
IPL [Member] | IPL's Duane Arnold Energy Center PPA amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	36	42
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	68	68
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	653	684
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	100	103
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	172	176
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	14	14
WPL [Member] | Asset retirement obligations [Member]
Regulatory Assets [Line Items]
Regulatory assets	35	34
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	95	108
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	64	68
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	44	44
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 129	$ 137