Investment in Securities (Summary of Investment in Securities) (Parenthetical) (Detail) - JPY (¥) ¥ in Millions |
Sep. 30, 2026 |
Mar. 31, 2026 |
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| Schedule of Investments [Line Items] | ||||
| Equity securities | ¥ 51,788 | ¥ 39,796 | ||
| Equity securities | [1] | 639,339 | 782,137 | |
| Investment Funds Elected for Fair Value Option | ||||
| Schedule of Investments [Line Items] | ||||
| Equity securities | 25,231 | 24,845 | ||
| Variable Annuity and Variable Life Insurance Contracts | ||||
| Schedule of Investments [Line Items] | ||||
| Equity securities | ¥ 146,898 | ¥ 137,933 | ||
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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