Due to Trust Account, Short-term Borrowings and Long-term Debt (Summary of Due to Trust Account Transactions) (Detail) - JPY (¥) ¥ in Millions |
Mar. 31, 2025 |
Mar. 31, 2024 |
|---|---|---|
| Debt Disclosure [Abstract] | ||
| Amount outstanding at end of fiscal year | ¥ 3,762,641 | ¥ 4,659,456 |
| Weighted average interest rate on outstanding balance at end of fiscal year | 0.10% | 0.00% |