v3.25.2
Regulatory Matters (Regulatory Assets) (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Regulatory Assets [Line Items]    
Regulatory assets $ 2,287 $ 2,274
Tax-related [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 1,030 989
AROs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 427 401
Pension and OPEB costs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 306 315
Assets retired early [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 167 180
Derivatives [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 57 60
Non-service pension and OPEB costs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 54 51
Commodity cost recovery [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 49 68
WPL's Western Wisconsin gas distribution expansion investments [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 40 42
Other [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 157 168
IPL [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 1,615 1,586
IPL [Member] | Tax-related [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 897 870
IPL [Member] | AROs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 296 281
IPL [Member] | Pension and OPEB costs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 153 157
IPL [Member] | Assets retired early [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 157 168
IPL [Member] | Derivatives [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 14 15
IPL [Member] | Non-service pension and OPEB costs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 20 19
IPL [Member] | Commodity cost recovery [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 10 2
IPL [Member] | Other [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 68 74
WPL [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 672 688
WPL [Member] | Tax-related [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 133 119
WPL [Member] | AROs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 131 120
WPL [Member] | Pension and OPEB costs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 153 158
WPL [Member] | Assets retired early [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 10 12
WPL [Member] | Derivatives [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 43 45
WPL [Member] | Non-service pension and OPEB costs [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 34 32
WPL [Member] | Commodity cost recovery [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 39 66
WPL [Member] | WPL's Western Wisconsin gas distribution expansion investments [Member]    
Regulatory Assets [Line Items]    
Regulatory assets 40 42
WPL [Member] | Other [Member]    
Regulatory Assets [Line Items]    
Regulatory assets $ 89 $ 94