Employee Benefits - Summary of Funding Requirement and Asset Ceiling (Detail) - Japanese Defined Benefit Plans [Member] - JPY (¥) ¥ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Disclosure of defined benefit plans [line items] | ||
| Beginning balance | ¥ 572,107 | ¥ 268,228 |
| Interest income | 13,542 | 4,694 |
| Change in asset ceiling excluding interest income | 133,201 | 299,185 |
| Ending balance | ¥ 718,851 | ¥ 572,107 |