Securitizations and Variable Interest Entities (VIE) - Narrative (Detail) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Organization, Consolidation and Presentation of Financial Statements [Abstract] | ||
| Asset-backed securitization notes issued during period | $ 9,600 | $ 7,400 |
| Initial receivable principal balance underlying asset-backed securitization notes issued during period | 10,500 | 8,000 |
| Cash to be remitted to trusts | $ 688 | $ 476 |