Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Regulatory Liabilities	$ 1,446	$ 1,623
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	501
Other Investments	$ 0	150
Document Period End Date	Dec. 31, 2023
Letters of Credit Outstanding, Amount	$ 106	$ 33
Public Utilities, Allowance for Funds Used During Construction, Rate	6.50%	6.50%	6.70%
Public Utilities, Allowance for Funds Used During Construction, Capitalized Interest	$ 13	$ 7	$ 8
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	$ 19	14	17
Depreciation expense rate	3.40%
Amortization of Intangible Assets	$ 61	$ 58	58
Public Utilities, Approved Return on Equity, Percentage	9.50%	9.50%
Regulatory Assets	$ 713	$ 527
Finite-Lived Intangible Assets, Accumulated Amortization	558	499
Future Amortization Expense, Year One	70
Future Amortization Expense, Year Two	58
Future Amortization Expense, Year Three	50
Future Amortization Expense, Year Four	45
Future Amortization Expense, Year Five	24
Power Cost Deadband - Lower Threshold	15
Power Cost Deadband - Upper Threshold	30
Quantifying Misstatement in Current Year Financial Statements, Amount	5,252	4,813
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	4,757	4,423
Asset Retirement Obligation, Cash Paid to Settle	25	27	18
Deferred Purchased Power Costs	5	23	62
Unbilled Receivables, Current	138	131
Excise Taxes Collected	56	53	48
Other Operating Activities, Cash Flow Statement	24	0	$ 0
Letter of Credit [Member]
Property, Plant and Equipment [Line Items]
Letters of Credit Outstanding, Amount	40
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	139	131
Asset Retirement Obligation Costs [Member]
Property, Plant and Equipment [Line Items]
Regulatory Liabilities	4	7
Deferred Income Tax Charge [Member]
Property, Plant and Equipment [Line Items]
Regulatory Liabilities	177	$ 194
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	$ 0