Borrowings and Other Financing Instruments, Commercial Paper (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Dec. 31, 2024 |
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| Short-term Debt [Line Items] | ||||
| Amount outstanding at period end | $ 0 | $ 35 | ||
| Credit Facility | ||||
| Short-term Debt [Line Items] | ||||
| Line of Credit Facility, Maximum Borrowing Capacity | [1] | 150 | ||
| Commercial Paper | ||||
| Short-term Debt [Line Items] | ||||
| Line of Credit Facility, Maximum Borrowing Capacity | 150 | 150 | ||
| Amount outstanding at period end | 0 | 35 | ||
| Average amount outstanding | 0 | 11 | ||
| Maximum amount outstanding | 0 | $ 99 | ||
| Weighted average interest rate, computed on a daily basis | 5.42% | |||
| Weighted average interest rate at period end | 4.59% | |||
| Money Pool | ||||
| Short-term Debt [Line Items] | ||||
| Line of Credit Facility, Maximum Borrowing Capacity | 150 | $ 150 | ||
| Amount outstanding at period end | 0 | 0 | ||
| Average amount outstanding | 5 | 4 | ||
| Maximum amount outstanding | $ 42 | $ 54 | ||
| Weighted average interest rate, computed on a daily basis | 4.33% | 5.34% | ||
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