Income Taxes - Changes in valuation allowance for deferred tax assets (Parenthetical) (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2024 |
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| Income Tax Disclosure [Abstract] | ||||||||||||
| Increase (decrease) of valuation allowances of certain foreign subsidiaries | ¥ (21,610) | ¥ 83,838 | ||||||||||
| Reduction of valuation allowances related to to valuation of financial instruments | 3,041 | 3,238 | ||||||||||
| Increase (decrease) in valuation allowances of certain foreign subsidiaries related to valuation of financial instruments | ¥ 12,691 | |||||||||||
| Increase (decrease) in valuation allowances of japanese subsidiaries and the company related to investments in subsidiaries and affiliates | 4,718 | |||||||||||
| Total, Net change during the year | ¥ 17,409 | [1] | ¥ (24,651) | [2] | ¥ 80,600 | [3] | ||||||
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