Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Assets:
Money market fund investments	$ 59	$ 32
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	7,972	8,330
IPL [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	3,738	4,124
WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,592	2,862
Commodity Contracts [Member]
Assets:
Derivatives	261	176
Liabilities:
Derivatives	7	9
Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	127	84
Liabilities:
Derivatives	4	4
Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	134	92
Liabilities:
Derivatives	3	5
Level 1 [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	0	0
Level 1 [Member] | IPL [Member]
Assets:
Money market fund investments	59	32
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 2 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	7,971	8,329
Level 2 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	0	0
Liabilities:
Long-term debt (incl. current maturities)	3,738	4,124
Level 2 [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,592	2,862
Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivatives	251	146
Liabilities:
Derivatives	7	8
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	120	65
Liabilities:
Derivatives	4	3
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	131	81
Liabilities:
Derivatives	3	5
Level 3 [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	1	1
Level 3 [Member] | IPL [Member]
Assets:
Money market fund investments	0	0
Deferred proceeds	227	214
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	30
Liabilities:
Derivatives	0	1
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	7	19
Liabilities:
Derivatives	0	1
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	3	11
Liabilities:
Derivatives	0	0
Carrying Amount [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	7,716	7,368
Carrying Amount [Member] | IPL [Member]
Assets:
Money market fund investments	59	32
Deferred proceeds	227	214
Liabilities:
Long-term debt (incl. current maturities)	3,644	3,643
Carrying Amount [Member] | WPL [Member]
Liabilities:
Long-term debt (incl. current maturities)	2,430	2,429
Carrying Amount [Member] | Commodity Contracts [Member]
Assets:
Derivatives	261	176
Liabilities:
Derivatives	7	9
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member]
Assets:
Derivatives	127	84
Liabilities:
Derivatives	4	4
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member]
Assets:
Derivatives	134	92
Liabilities:
Derivatives	$ 3	$ 5