Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative [Line Items]
Interest rate swap	$ 9,109	$ 8,143
Non-current interest rate swap assets	177	227
Accumulated other comprehensive income	1	0
Interest expense, interest rate swap	394	325	$ 277
IPL [Member]
Derivative [Line Items]
Interest rate swap	3,975	3,675
Non-current interest rate swap assets	84	110
Interest expense, interest rate swap	155	148	139
WPL [Member]
Derivative [Line Items]
Interest rate swap	3,100	2,800
Non-current interest rate swap assets	61	98
Interest expense, interest rate swap	149	$ 121	$ 105
Alliant Energy Finance, LLC [Member] | Interest Rate Swap | Term Loan Credit Agreement [Member]
Derivative [Line Items]
Interest rate swap	$ 300
Interest rate swap, fixed interest rate percentage	3.93%
Non-current interest rate swap assets	$ 1
Accumulated other comprehensive income	1
Interest expense, interest rate swap	$ 3