Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 7	$ (5)	$ 24	$ 19
Total net gains (losses) included in changes in net assets (realized/unrealized)	(5)	(7)	(8)	(11)
Purchases	59	62	59	62
Sales	(1)	(1)	(1)	(1)
Settlements	(9)	5	(23)	(15)
Ending balance	51	54	51	54
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	(5)	(7)	(8)	(11)
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	5	0	19	16
Total net gains (losses) included in changes in net assets (realized/unrealized)	(2)	(13)	(6)	(12)
Purchases	45	51	45	51
Sales	(1)	(1)	(1)	(1)
Settlements	(7)	4	(17)	(13)
Ending balance	40	41	40	41
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	(2)	(13)	(6)	(12)
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	2	(5)	5	3
Total net gains (losses) included in changes in net assets (realized/unrealized)	(3)	6	(2)	1
Purchases	14	11	14	11
Settlements	(2)	1	(6)	(2)
Ending balance	11	13	11	13
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	(3)	6	(2)	1
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	184	153	216	185
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	(13)	22	(45)	(10)
Ending balance	171	175	171	175
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	184	153	216	185
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	(13)	22	(45)	(10)
Ending balance	171	175	171	175
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