Balance Sheet Components (Details) $ in Millions	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss	$ 22			$ 23	$ 22		$ 26
Unbilled Receivables, Current	98				98		117
Finite-Lived Intangible Assets, Accumulated Amortization	485				485		446
Amortization of Intangible Assets	15		$ 14		44
Line of Credit Facility, Maximum Borrowing Capacity	$ 750				$ 750
Debt Instrument, Covenant Description					65.00%
Ratio of Indebtedness to Net Capital	0.548				0.548
Line of Credit Facility, Remaining Borrowing Capacity	$ 650				$ 650
Line of Credit Facility, Current Borrowing Capacity	220		650		220	$ 650
Authorized Short-Term Debt	900				900
Purchased power and fuel	337		$ 259		707	613
Repayments of Long-term Debt					0	$ 160
Operating Lease, Right-of-Use Asset	29				29
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	30				30
Amount above baseline net variable power costs		$ 62			(2)
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
Letters of Credit Outstanding, Amount	91				91
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				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	30				30		29
Fire
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	31				31		45
pandemic
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	34				34		$ 36
Letter of Credit [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Commercial paper	$ 40				$ 40