Fair Value of Financial Assets and Liabilities - Reconciliations for Financial Assets and Liabilities Carried at Fair Value (Parenthetical) (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Disclosure of detailed information about financial instruments [line items] | ||
| Transfers into Level 3 | ¥ 72,155 | ¥ 39,417 |
| Transfers out of Level 3 | ¥ 2,297 | ¥ 6,634 |