Commitments and Contingencies - Narrative (Detail) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Commitments And Contingencies Disclosure [Line Items] | ||
| Lease expense under operating leases | $ 2 | $ 2 |
| Operating lease, weighted average remaining lease term | 6 years 4 months 24 days | |
| Operating lease, weighted average discount rate (percentage) | 3.00% | |
| Revolving lines of credit | ||
| Commitments And Contingencies Disclosure [Line Items] | ||
| Unused balance of commercial revolving lines of credit | $ 737 | |
| Construction of auto dealership facilities | ||
| Commitments And Contingencies Disclosure [Line Items] | ||
| Remaining unfunded balance for construction loans | $ 3 | |