v3.25.2
Fair Value Measurements (Fair Value Measurements) (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Carrying Amount [Member]    
Assets:    
Money market fund investments and time deposits $ 303 $ 52
Deferred proceeds 235 163
Liabilities:    
Long-term debt (incl. current maturities) 11,015 9,848
Carrying Amount [Member] | IPL [Member]    
Assets:    
Money market fund investments and time deposits 194 9
Deferred proceeds 235 163
Liabilities:    
Long-term debt (incl. current maturities) 4,684 4,090
Carrying Amount [Member] | WPL [Member]    
Assets:    
Money market fund investments and time deposits 0 43
Liabilities:    
Long-term debt (incl. current maturities) 3,371 3,370
Carrying Amount [Member] | Commodity Contracts [Member]    
Assets:    
Derivatives 105 75
Liabilities:    
Derivatives 53 58
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]    
Assets:    
Derivatives 69 48
Liabilities:    
Derivatives 12 13
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]    
Assets:    
Derivatives 36 27
Liabilities:    
Derivatives 41 45
Money market fund investments and time deposits 303 52
Deferred proceeds 235 163
Long-term debt (incl. current maturities) 10,617 9,577
IPL [Member]    
Assets:    
Money market fund investments and time deposits 194 9
Deferred proceeds 235 163
Liabilities:    
Long-term debt (incl. current maturities) 4,408 3,736
WPL [Member]    
Assets:    
Money market fund investments and time deposits 0 43
Liabilities:    
Long-term debt (incl. current maturities) 3,238 3,170
Commodity Contracts [Member]    
Assets:    
Derivatives 105 75
Liabilities:    
Derivatives 53 58
Commodity Contracts [Member] | IPL [Member]    
Assets:    
Derivatives 69 48
Liabilities:    
Derivatives 12 13
Commodity Contracts [Member] | WPL [Member]    
Assets:    
Derivatives 36 27
Liabilities:    
Derivatives 41 45
Level 1 [Member]    
Assets:    
Money market fund investments and time deposits 303 52
Deferred proceeds 0 0
Liabilities:    
Long-term debt (incl. current maturities) 0 0
Level 1 [Member] | IPL [Member]    
Assets:    
Money market fund investments and time deposits 194 9
Deferred proceeds 0 0
Liabilities:    
Long-term debt (incl. current maturities) 0 0
Level 1 [Member] | WPL [Member]    
Assets:    
Money market fund investments and time deposits 0 43
Liabilities:    
Long-term debt (incl. current maturities) 0 0
Level 1 [Member] | Commodity Contracts [Member]    
Assets:    
Derivatives 0 0
Liabilities:    
Derivatives 0 0
Level 1 [Member] | Commodity Contracts [Member] | IPL [Member]    
Assets:    
Derivatives 0 0
Liabilities:    
Derivatives 0 0
Level 1 [Member] | Commodity Contracts [Member] | WPL [Member]    
Assets:    
Derivatives 0 0
Liabilities:    
Derivatives 0 0
Level 2 [Member]    
Assets:    
Money market fund investments and time deposits 0 0
Deferred proceeds 0 0
Liabilities:    
Long-term debt (incl. current maturities) 10,617 9,577
Level 2 [Member] | IPL [Member]    
Assets:    
Money market fund investments and time deposits 0 0
Deferred proceeds 0 0
Liabilities:    
Long-term debt (incl. current maturities) 4,408 3,736
Level 2 [Member] | WPL [Member]    
Assets:    
Money market fund investments and time deposits 0 0
Liabilities:    
Long-term debt (incl. current maturities) 3,238 3,170
Level 2 [Member] | Commodity Contracts [Member]    
Assets:    
Derivatives 48 48
Liabilities:    
Derivatives 52 56
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]    
Assets:    
Derivatives 24 26
Liabilities:    
Derivatives 11 11
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]    
Assets:    
Derivatives 24 22
Liabilities:    
Derivatives 41 45
Level 3 [Member]    
Assets:    
Money market fund investments and time deposits 0 0
Deferred proceeds 235 163
Liabilities:    
Long-term debt (incl. current maturities) 0 0
Level 3 [Member] | IPL [Member]    
Assets:    
Money market fund investments and time deposits 0 0
Deferred proceeds 235 163
Liabilities:    
Long-term debt (incl. current maturities) 0 0
Level 3 [Member] | WPL [Member]    
Assets:    
Money market fund investments and time deposits 0 0
Liabilities:    
Long-term debt (incl. current maturities) 0 0
Level 3 [Member] | Commodity Contracts [Member]    
Assets:    
Derivatives 57 27
Liabilities:    
Derivatives 1 2
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]    
Assets:    
Derivatives 45 22
Liabilities:    
Derivatives 1 2
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]    
Assets:    
Derivatives 12 5
Liabilities:    
Derivatives $ 0 $ 0