Short-Term Debt - Credit Facilities (Detail) - USD ($) |
Jun. 30, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Line Of Credit Facility [Line Items] | ||
| Borrowings Outstanding | $ 464,000,000 | $ 636,000,000 |
| Credit Facility [Member] | December 1, 2028 [Member] | ||
| Line Of Credit Facility [Line Items] | ||
| Credit Facilities | 800,000,000 | 800,000,000 |
| Letters of Credit Outstanding | 1,000,000 | 1,000,000 |
| Credit Facility [Member] | December 1, 2028 [Member] | Credit Facilities [Member] | ||
| Line Of Credit Facility [Line Items] | ||
| Borrowings Outstanding | 0 | 0 |
| Credit Facility [Member] | December 1, 2028 [Member] | Commercial Paper [Member] | ||
| Line Of Credit Facility [Line Items] | ||
| Borrowings Outstanding | $ 464,000,000 | $ 636,000,000 |