Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,324.0	$ 1,271.0
Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	579.0	585.0
Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	398.0	384.0
Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	210.0	166.0
Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	40.0	17.0
West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	32.0	36.0
Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	20.0	51.0
Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	45.0	32.0
IPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	754.0	691.0
IPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	303.0	312.0
IPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	259.0	252.0
IPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	115.0	77.0
IPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	38.0	15.0
IPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	10.0	27.0
IPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	29.0	8.0
WPL [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	570.0	580.0
WPL [Member] | Tax-related [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	276.0	273.0
WPL [Member] | Cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	139.0	132.0
WPL [Member] | Derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	95.0	89.0
WPL [Member] | Commodity cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	2.0	2.0
WPL [Member] | West Riverside liquidated damages [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	32.0	36.0
WPL [Member] | Electric transmission cost recovery [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	10.0	24.0
WPL [Member] | Other [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 16.0	$ 24.0