Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Assets:
Money market fund investments	$ 189	$ 10
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	7,863	7,339
IPL [Member]
Assets:
Money market fund investments	180	10
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	3,422	3,228
WPL [Member]
Assets:
Money market fund investments	9
Liabilities:
Long-term debt (incl. current maturities)	2,722	2,542
Commodity Contracts [Member]
Assets:
Derivatives	129	237
Liabilities:
Derivatives	66	79
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	85	138
Liabilities:
Derivatives	21	46
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	44	99
Liabilities:
Derivatives	45	33
Interest Rate Swap [Member]
Assets:
Derivatives	6	0
Level 1 [Member]
Assets:
Money market fund investments	189	10
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Money market fund investments	180	10
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)	7,863	7,338
Level 2 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	3,422	3,228
Level 2 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,722	2,542
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	80	206
Liabilities:
Derivatives	60	67
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	45	111
Liabilities:
Derivatives	16	35
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	35	95
Liabilities:
Derivatives	44	32
Level 2 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	6	0
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	0	1
Level 3 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	236	185
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	49	31
Liabilities:
Derivatives	6	12
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	40	27
Liabilities:
Derivatives	5	11
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	9	4
Liabilities:
Derivatives	1	1
Level 3 [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	0	0
Carrying Amount [Member]
Assets:
Money market fund investments	189	10
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	8,838	8,076
Carrying Amount [Member] | IPL [Member]
Assets:
Money market fund investments	180	10
Deferred proceeds	236	185
Liabilities:
Long-term debt (incl. current maturities)	3,944	3,646
Carrying Amount [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	3,069	2,770
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	129	237
Liabilities:
Derivatives	66	79
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	85	138
Liabilities:
Derivatives	21	46
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	44	99
Liabilities:
Derivatives	45	33
Carrying Amount [Member] | Interest Rate Swap [Member]
Assets:
Derivatives	$ 6	$ 0