Balance Sheet Components (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss	$ 28		$ 26
Unbilled Receivables, Current	90		117
Finite-Lived Intangible Assets, Accumulated Amortization	457		446
Amortization of Intangible Assets		$ 15
Line of Credit Facility, Maximum Borrowing Capacity	$ 750
Debt Instrument, Covenant Description	65.00%
Ratio of Indebtedness to Net Capital	0.560
Line of Credit Facility, Remaining Borrowing Capacity	$ 650
Line of Credit Facility, Current Borrowing Capacity	220	650
Authorized Short-Term Debt	900
Purchased power and fuel	202	169
Repayments of Long-term Debt	0	140
Operating Lease, Right-of-Use Asset	29
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	28
Amount above baseline net variable power costs	(10)		62
Lower deadband limit below baseline net variable power costs	15
Upper deadband limit above baseline net variable power costs	30
Proceeds from failed sale-leaseback transactions	25	$ 0
Letters of Credit Outstanding, Amount	75
Sale Leaseback Transaction, Net Book Value			37
Gain (Loss) on Disposition of Intangible Assets	11
Gain (Loss) on Disposition of Property Plant Equipment	1
Asset Impairment Charges	17
Increase (Decrease) in Deferred Charges	15
Tangible Asset Impairment Charges	2
Finance Lease, Liability	25
221119 Other Electric Power Generation
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	28		29
Fire
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	38		45
pandemic
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	35		$ 36
Letter of Credit [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Commercial paper	$ 0