Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (5)	$ 10	$ 19	$ 29
Total net gains (losses) included in changes in net assets (realized/unrealized)	(7)	(10)	(11)	(16)
Purchases	62	79	62	79
Sales	(1)	0	(1)	0
Settlements	5	(7)	(15)	(20)
Ending balance	54	72	54	72
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 June 30	(7)	(10)	(11)	(16)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	7	16	18
Total net gains (losses) included in changes in net assets (realized/unrealized)	(13)	(3)	(12)	(7)
Purchases	51	58	51	58
Sales	(1)	0	(1)	0
Settlements	4	(4)	(13)	(11)
Ending balance	41	58	41	58
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 June 30	(13)	(3)	(12)	(8)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(5)	3	3	11
Total net gains (losses) included in changes in net assets (realized/unrealized)	6	(7)	1	(9)
Purchases	11	21	11	21
Settlements	1	(3)	(2)	(9)
Ending balance	13	14	13	14
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 June 30	6	(7)	1	(8)
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	153	227	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	22	17	(10)	30
Ending balance	175	244	175	244
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 June 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	153	227	185	214
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	22	17	(10)	30
Ending balance	175	244	175	244
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 June 30	$ 0	$ 0	$ 0	$ 0