Income Tax - Summary of Deductible Temporary Differences and Carryforward of Unused Tax Losses for which Deferred Tax Assets are not Recognized (Details) - JPY (¥) ¥ in Millions |
Mar. 31, 2026 |
Mar. 31, 2025 |
|---|---|---|
| Income Tax [Abstract] | ||
| Deductible temporary differences | ¥ 59,507 | ¥ 135,389 |
| Carryforward of unused tax losses | 20,350 | 141,868 |
| Total | ¥ 79,857 | ¥ 277,257 |