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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 |  |

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