Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,372	$ 1,271
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	578	585
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	391	384
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	258	166
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	50	51
WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	35	36
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	60	49
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	754	691
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	310	312
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	256	252
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	125	77
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	29	27
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	34	23
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	618	580
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	268	273
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	135	132
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	133	89
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	21	24
WPL [Member] | WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	35	36
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 26	$ 26