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Fair Value Measurements - Additional Information (Detail) - Fair Value, Measurements, Recurring - JPY (¥) ¥ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Transfers in or out of Level 3 | ¥ 0 | ¥ 0 |  | ¥ 0
Foreign municipal bond securities |  |  |  |
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items] |  |  |  |
Transferred from level 2 to level 3 |  |  | ¥ 1,273 |

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- Definition Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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