Employee benefit plans - Net periodic benefit cost for defined benefit plans (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | ||
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Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2024 |
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| Employee Benefit Plans [Abstract] | |||
| Service cost | ¥ 5,404 | ¥ 5,748 | ¥ 6,028 |
| Interest cost | 5,056 | 4,039 | 3,484 |
| Expected return on plan assets | (5,369) | (5,664) | (5,658) |
| Amortization of net actuarial losses | 798 | 1,844 | 3,021 |
| Amortization of prior service cost | (541) | (441) | (1,603) |
| Net periodic benefit cost | ¥ 5,348 | ¥ 5,526 | ¥ 5,272 |
| Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] | Labor and Related Expense | Labor and Related Expense | Labor and Related Expense |
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- References No definition available.
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- Definition Amount of gain (loss), recognized immediately as component of net periodic benefit (cost) credit, for change in value of benefit obligation or plan assets from experience different from that assumed, change in actuarial assumption, or consequence of temporarily deviating from substantive plan. Includes, but is not limited to, amount in excess of 10 percent of greater of fair value of plan assets or benefit obligation. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of cost recognized for passage of time related to defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of net periodic benefit cost (credit) for defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Indicates line item in statement of income or comprehensive income that includes components of net periodic benefit cost (credit), excluding service cost component, for defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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