Derivative Financial Instruments and Hedge Accounting - Schedule of Hedges of Net Investments in Foreign Operations (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Foreign exchange forward contracts [member] | Derivative Financial Instruments-Net [Member] | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Notional amounts | ¥ 3,835,799 | ¥ 3,626,636 |
| Carrying amounts, Assets | 37,235 | 34,176 |
| Carrying amounts, Liabilities | 297,585 | 110,254 |
| Change in value used for calculating hedge ineffectiveness | (268,646) | (14,745) |
| Foreign currency denominated financial liabilities [member] | Debt securities, borrowed money, deposits [member] | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Notional amounts | 227,322 | 212,580 |
| Carrying amounts, Assets | ||
| Carrying amounts, Liabilities | 227,322 | 212,580 |
| Change in value used for calculating hedge ineffectiveness | ¥ (14,742) | ¥ 2,558 |