Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Carrying Amount [Member]
Assets:
Money market fund investments	$ 10	$ 45
Deferred proceeds	184	216
Liabilities:
Long-term debt (incl. current maturities)	9,333	9,034
Carrying Amount [Member] | IPL [Member]
Assets:
Money market fund investments	6	45
Deferred proceeds	184	216
Liabilities:
Long-term debt (incl. current maturities)	3,945	3,945
Carrying Amount [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	3,367	3,070
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	56	88
Liabilities:
Derivatives	94	98
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	34	54
Liabilities:
Derivatives	30	30
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	22	34
Liabilities:
Derivatives	64	68
Carrying Amount [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	3	1
Money market fund investments	10	45
Deferred proceeds	184	216
Liabilities:
Long-term debt (incl. current maturities)	9,051	8,677
IPL [Member]
Assets:
Money market fund investments	6	45
Deferred proceeds	184	216
Liabilities:
Long-term debt (incl. current maturities)	3,607	3,664
WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	3,176	2,933
Commodity Contracts [Member]
Assets:
Derivatives	56	88
Liabilities:
Derivatives	94	98
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	34	54
Liabilities:
Derivatives	30	30
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	22	34
Liabilities:
Derivatives	64	68
Interest Rate Swap [Member]
Assets:
Derivatives	3	1
Level 1 [Member]
Assets:
Money market fund investments	10	45
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Money market fund investments	6	45
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | WPL [Member]
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
Level 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	9,051	8,677
Level 2 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	3,607	3,664
Level 2 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	3,176	2,933
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	46	59
Liabilities:
Derivatives	91	93
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	26	30
Liabilities:
Derivatives	27	25
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	20	29
Liabilities:
Derivatives	64	68
Level 2 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	3	1
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	184	216
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	184	216
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 3 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	10	29
Liabilities:
Derivatives	3	5
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	8	24
Liabilities:
Derivatives	3	5
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	2	5
Liabilities:
Derivatives	0	0
Level 3 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	$ 0	$ 0