Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Regulatory Liabilities	$ 1,466	$ 1,392
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	322
Other Investments	$ 44	255
Document Period End Date	Dec. 31, 2021
Letters of Credit Outstanding, Amount	$ 18	$ 12
Public Utilities, Allowance for Funds Used During Construction, Rate	6.70%	6.90%	7.10%
Public Utilities, Allowance for Funds Used During Construction, Capitalized Interest	$ 8	$ 8	$ 5
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	$ 17	$ 16	$ 10
Depreciation expense rate	3.40%	3.50%	3.60%
Amortization of Intangible Assets	$ 58	$ 64	$ 64
Public Utilities, Approved Return on Equity, Percentage	9.50%	9.50%	9.50%
Regulatory Assets	$ 557	$ 592
Finite-Lived Intangible Assets, Accumulated Amortization	446	388
Future Amortization Expense, Year One	59
Future Amortization Expense, Year Two	51
Future Amortization Expense, Year Three	46
Future Amortization Expense, Year Four	33
Future Amortization Expense, Year Five	25
Power Cost Deadband - Lower Threshold	15
Power Cost Deadband - Upper Threshold	30
Quantifying Misstatement in Current Year Financial Statements, Amount	4,469	4,136
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	4,146	3,864
Trading Gain (Loss)		127
Asset Retirement Obligation, Cash Paid to Settle	18	18	$ 9
Deferred Purchased Power Costs	62	13
Unbilled Receivables, Current	117	97
Excise Taxes Collected	48	46	$ 45
Trojan decommissioning [Member]
Property, Plant and Equipment [Line Items]
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	90	88
Asset Retirement Obligation Costs [Member]
Property, Plant and Equipment [Line Items]
Regulatory Liabilities	43	37
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	0
Deferred Income Tax Charge [Member]
Property, Plant and Equipment [Line Items]
Regulatory Liabilities	208	$ 239
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	$ 0