Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,187	$ 1,324
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	569	579
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	397	398
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	91	210
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	41	40
WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	9	32
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	6	20
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	74	45
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	655	754
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	301	303
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	249	259
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	52	115
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	11	38
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	6	10
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	36	29
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	532	570
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	268	276
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	148	139
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	39	95
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	30	2
WPL [Member] | WPL's West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	9	32
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	0	10
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 38	$ 16