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Pension Plans (Net Pension Cost of Defined Benefit Plans) (Detail) - JPY (¥) ¥ in Millions | 6 Months Ended
--- | ---
Sep. 30, 2025 | Sep. 30, 2024
Japanese plans |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Service cost | ¥ 2,222 | ¥ 2,584
Interest cost | 975 | 704
Expected return on plan assets | (1,372) | (1,397)
Amortization of prior service credit | (32) | (36)
Amortization of net actuarial loss | (69) | (49)
Net periodic pension cost | 1,724 | 1,806
Overseas plans |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Service cost | 1,371 | 1,654
Interest cost | 2,302 | 2,070
Expected return on plan assets | (3,601) | (3,535)
Amortization of prior service credit | (137) | (162)
Amortization of net actuarial loss | (2) | 2
Amortization of transition obligation | 0 | 1
Net periodic pension cost | ¥ (67) | ¥ 30

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