Balance Sheet Components Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	$ 14		$ 14		$ 23
Regulatory assets - noncurrent	567		567		569
Regulatory Liability, Current	187		187		23
Regulatory liabilities-noncurrent	1,370		1,370		1,369
Purchased power and fuel	259	$ 292	613	$ 554
Removal Costs [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	0		0		0
Regulatory liabilities-noncurrent	1,035		1,035		1,016
Deferred Income Tax Charge [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	0		0		0
Regulatory liabilities-noncurrent	213		213		239
Asset Retirement Obligation Costs [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	0		0		0
Regulatory liabilities-noncurrent	54		54		37
Revenue Subject to Refund [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities-noncurrent	0		0		0
Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	32		32		5
Regulatory liabilities-noncurrent	68		68		77
Regulatory Clause Revenues, under-recovered
Regulatory Assets and Liabilities [Line Items]
Regulatory Liability, Current	155		155		18
Deferred Derivative Gain (Loss) [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	0		0		0
Regulatory assets - noncurrent	11		11		124
Pension and Other Postretirement Plans Costs [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	0		0		0
Regulatory assets - noncurrent	223		223		240
Loss on Reacquired Debt [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	0		0		0
Regulatory assets - noncurrent	24		24		25
Environmental Restoration Costs [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	0		0		0
Regulatory assets - noncurrent	99		99		95
Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets, Current	14		14		23
Regulatory assets - noncurrent	62		62		60
Storm Costs
Regulatory Assets and Liabilities [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	58		58
221119 Other Electric Power Generation
Regulatory Assets and Liabilities [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	27		27		0
Fire
Regulatory Assets and Liabilities [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	36		36		15
pandemic
Regulatory Assets and Liabilities [Line Items]
Increase (Decrease) in Accounts Payable and Other Operating Liabilities	$ 27		$ 27		$ 10