Balance Sheet Components (Details) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss	$ 23	$ 28		$ 23		$ 26
Unbilled Receivables, Current	94			94		117
Finite-Lived Intangible Assets, Accumulated Amortization	470			470		446
Amortization of Intangible Assets	14		$ 15	29	$ 30
Line of Credit Facility, Maximum Borrowing Capacity	$ 750			$ 750
Debt Instrument, Covenant Description				65.00%
Ratio of Indebtedness to Net Capital	0.556			0.556
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	168		$ 185	370	354
Repayments of Long-term Debt				0	140
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				(32)		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	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	30			30		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	$ 0			$ 0