Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Carrying Amount [Member]
Assets:
Time deposits and/or money market fund investments	$ 803	$ 45
Deferred proceeds	212	216
Liabilities:
Long-term debt (incl. current maturities)	10,349	9,034
Carrying Amount [Member] | IPL [Member]
Assets:
Time deposits and/or money market fund investments	745	45
Deferred proceeds	212	216
Liabilities:
Long-term debt (incl. current maturities)	4,589	3,945
Carrying Amount [Member] | WPL [Member]
Assets:
Time deposits and/or money market fund investments	58	0
Liabilities:
Long-term debt (incl. current maturities)	3,369	3,070
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	82	88
Liabilities:
Derivatives	76	98
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	55	54
Liabilities:
Derivatives	20	30
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	27	34
Liabilities:
Derivatives	56	68
Carrying Amount [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	0	1
Liabilities:
Derivatives	1	0
Time deposits and/or money market fund investments	803	45
Deferred proceeds	212	216
Long-term debt (incl. current maturities)	10,444	8,677
IPL [Member]
Assets:
Time deposits and/or money market fund investments	745	45
Deferred proceeds	212	216
Liabilities:
Long-term debt (incl. current maturities)	4,407	3,664
WPL [Member]
Assets:
Time deposits and/or money market fund investments	58	0
Liabilities:
Long-term debt (incl. current maturities)	3,322	2,933
Commodity Contracts [Member]
Assets:
Derivatives	82	88
Liabilities:
Derivatives	76	98
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	55	54
Liabilities:
Derivatives	20	30
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	27	34
Liabilities:
Derivatives	56	68
Interest Rate Swap [Member]
Assets:
Derivatives	0	1
Liabilities:
Derivatives	1	0
Level 1 [Member]
Assets:
Time deposits and/or money market fund investments	803	45
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Time deposits and/or money market fund investments	745	45
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | WPL [Member]
Assets:
Time deposits and/or money market fund investments	58	0
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 1 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Level 2 [Member]
Assets:
Time deposits and/or money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	10,444	8,677
Level 2 [Member] | IPL [Member]
Assets:
Time deposits and/or money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	4,407	3,664
Level 2 [Member] | WPL [Member]
Assets:
Time deposits and/or money market fund investments	0	0
Liabilities:
Long-term debt (incl. current maturities)	3,322	2,933
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	42	59
Liabilities:
Derivatives	73	93
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	23	30
Liabilities:
Derivatives	17	25
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	19	29
Liabilities:
Derivatives	56	68
Level 2 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	0	1
Liabilities:
Derivatives	1	0
Level 3 [Member]
Assets:
Time deposits and/or money market fund investments	0	0
Deferred proceeds	212	216
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | IPL [Member]
Assets:
Time deposits and/or money market fund investments	0	0
Deferred proceeds	212	216
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | WPL [Member]
Assets:
Time deposits and/or money market fund investments	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	40	29
Liabilities:
Derivatives	3	5
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	32	24
Liabilities:
Derivatives	3	5
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	8	5
Liabilities:
Derivatives	0	0
Level 3 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	0	0
Liabilities:
Derivatives	$ 0	$ 0