Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 51	$ 54	$ 24	$ 19
Total net gains (losses) included in changes in net assets (realized/unrealized)	2	17	(7)	6
Purchases			59	62
Sales	0	(1)	(1)	(2)
Settlements	(16)	(27)	(38)	(42)
Ending balance	37	43	37	43
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	2	17	(7)	6
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	40	41	19	16
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	12	(7)	0
Purchases			45	51
Sales	0	(1)	(1)	(2)
Settlements	(11)	(17)	(27)	(30)
Ending balance	29	35	29	35
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	12	(7)	0
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	11	13	5	3
Total net gains (losses) included in changes in net assets (realized/unrealized)	2	5	0	6
Purchases			14	11
Settlements	(5)	(10)	(11)	(12)
Ending balance	8	8	8	8
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	2	5	0	6
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	171	175	216	185
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	41	61	(4)	51
Ending balance	212	236	212	236
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	171	175	216	185
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	41	61	(4)	51
Ending balance	212	236	212	236
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