Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 19	$ 29
Total net gains (losses) included in changes in net assets (realized/unrealized)	(4)	(6)
Settlements	(20)	(13)
Ending balance	(5)	10
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	(4)	(5)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	16	18
Total net gains (losses) included in changes in net assets (realized/unrealized)	1	(4)
Settlements	(17)	(7)
Ending balance	0	7
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	1	(4)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	3	11
Total net gains (losses) included in changes in net assets (realized/unrealized)	(5)	(2)
Settlements	(3)	(6)
Ending balance	(5)	3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	(5)	(1)
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0
Settlements	(32)	13
Ending balance	153	227
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	0	0
Deferred Proceeds [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0
Settlements	(32)	13
Ending balance	153	227
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31	$ 0	$ 0