Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Regulatory Assets [Line Items]
Regulatory assets	$ 2,350	$ 2,261
Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,000	934
Asset retirement obligations (AROs) [Member]
Regulatory Assets [Line Items]
Regulatory assets	418	194
Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	329	347
Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	181	273
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	80	102
Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	76	120
WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	42	44
IPL's Duane Arnold Energy Center purchased power agreement amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	24	42
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	200	205
IPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,568	1,577
IPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	885	831
IPL [Member] | Asset retirement obligations (AROs) [Member]
Regulatory Assets [Line Items]
Regulatory assets	223	160
IPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	163	171
IPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	169	259
IPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	24	34
IPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	8	12
IPL [Member] | IPL's Duane Arnold Energy Center purchased power agreement amendment [Member]
Regulatory Assets [Line Items]
Regulatory assets	24	42
IPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	72	68
WPL [Member]
Regulatory Assets [Line Items]
Regulatory assets	782	684
WPL [Member] | Tax-related [Member]
Regulatory Assets [Line Items]
Regulatory assets	115	103
WPL [Member] | Asset retirement obligations (AROs) [Member]
Regulatory Assets [Line Items]
Regulatory assets	195	34
WPL [Member] | Pension and OPEB costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	166	176
WPL [Member] | Assets retired early [Member]
Regulatory Assets [Line Items]
Regulatory assets	12	14
WPL [Member] | Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory assets	56	68
WPL [Member] | Commodity cost recovery [Member]
Regulatory Assets [Line Items]
Regulatory assets	68	108
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]
Regulatory Assets [Line Items]
Regulatory assets	42	44
WPL [Member] | Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 128	$ 137