Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 54	$ 72	$ 19	$ 29
Total net gains (losses) included in changes in net assets (realized/unrealized)	17	(1)	6	(17)
Purchases			62	79
Sales	(1)	0	(2)	0
Settlements	(27)	(26)	(42)	(46)
Ending balance	43	45	43	45
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 September 30	17	(1)	6	(17)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	41	58	16	18
Total net gains (losses) included in changes in net assets (realized/unrealized)	12	(6)	0	(13)
Purchases			51	58
Sales	(1)	0	(2)	0
Settlements	(17)	(19)	(30)	(30)
Ending balance	35	33	35	33
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 September 30	12	(6)	0	(14)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	13	14	3	11
Total net gains (losses) included in changes in net assets (realized/unrealized)	5	5	6	(4)
Purchases			11	21
Settlements	(10)	(7)	(12)	(16)
Ending balance	8	12	8	12
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 September 30	5	5	6	(3)
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	175	244	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Purchases			0	0
Sales	0	0	0	0
Settlements	61	4	51	34
Ending balance	236	248	236	248
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 September 30	0	0	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	175	244	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Purchases			0	0
Sales	0	0	0	0
Settlements	61	4	51	34
Ending balance	236	248	236	248
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 September 30	$ 0	$ 0	$ 0	$ 0