Short-Term Borrowings and Long-Term Debt (Details of Other Short-Term Borrowings) (Detail) - JPY (¥) ¥ in Millions |
Mar. 31, 2026 |
Mar. 31, 2025 |
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|---|---|---|---|---|---|---|
| Short-term Debt [Line Items] | ||||||
| Borrowings from the Bank of Japan | ¥ 214,052 | ¥ 2,270,980 | ||||
| Other | 262,607 | 404,119 | ||||
| Total | 2,922,999 | 5,537,351 | ||||
| Mizuho Financial Group, Inc. | ||||||
| Short-term Debt [Line Items] | ||||||
| Commercial paper and short-term notes issued | [1],[2] | 2,275,299 | 2,705,133 | |||
| Consolidated VIEs | ||||||
| Short-term Debt [Line Items] | ||||||
| Commercial paper and short-term notes issued | [1] | 171,041 | 157,118 | |||
| Total | ¥ 277,787 | ¥ 401,275 | ||||
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