Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,130.0	$ 1,324.0
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	566.0	579.0
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	366.0	398.0
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	65.0	210.0
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	48.0	40.0
West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	1.0	32.0
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	84.0	65.0
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	644.0	754.0
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	299.0	303.0
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	242.0	259.0
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	34.0	115.0
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	13.0	38.0
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	56.0	39.0
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	486.0	570.0
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	267.0	276.0
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	124.0	139.0
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	31.0	95.0
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	35.0	2.0
WPL [Member] | West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	1.0	32.0
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 28.0	$ 26.0