Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,271	$ 1,306
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	585	732
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	384	367
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	166	28
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	51	68
WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	36	38
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	49	73
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	691	676
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	312	331
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	252	238
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	77	25
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	27	39
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	23	43
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	580	630
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	273	401
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	132	129
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	89	3
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	24	29
WPL [Member] | WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	36	38
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 26	$ 30