Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Commodity Contracts [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 72	$ 39	$ 29	$ 29
Total net gains (losses) included in changes in net assets (realized/unrealized)	(1)	5	(17)	6
Transfers out of Level 3	0	(8)	0	(8)
Purchases			79	21
Settlements	(26)	(7)	(46)	(19)
Ending balance	45	29	45	29
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	(1)	5	(17)	6
Commodity Contracts [Member] | IPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	58	30	18	26
Total net gains (losses) included in changes in net assets (realized/unrealized)	(6)	2	(13)	0
Transfers out of Level 3	0	(8)	0	(8)
Purchases			58	16
Settlements	(19)	(5)	(30)	(15)
Ending balance	33	19	33	19
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	(6)	2	(14)	0
Commodity Contracts [Member] | WPL [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	14	9	11	3
Total net gains (losses) included in changes in net assets (realized/unrealized)	5	3	(4)	6
Purchases			21	5
Settlements	(7)	(2)	(16)	(4)
Ending balance	12	10	12	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 September 30	5	3	(3)	6
Deferred Proceeds [Member]
Fair Value, Assets and Liabilities, Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	244	154	214	188
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Transfers out of Level 3	0	0	0	0
Purchases			0	0
Settlements	4	10	34	(24)
Ending balance	248	164	248	164
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	244	154	214	188
Total net gains (losses) included in changes in net assets (realized/unrealized)	0	0	0	0
Transfers out of Level 3	0	0	0	0
Purchases			0	0
Settlements	4	10	34	(24)
Ending balance	248	164	248	164
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