Derivative Financial Instruments and Hedging (Effect of Derivative Instruments on Consolidated Statements of Income, Pre-tax) (Detail) - Fair value hedges - JPY (¥) ¥ in Millions	6 Months Ended
Sep. 30, 2026	Sep. 30, 2025
Life insurance premiums and related investment income \| Interest rate swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in income	¥ 0
Life insurance premiums and related investment income \| Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in income	8,285	¥ 8,761
Interest expense \| Interest rate swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in income	0
Interest expense \| Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in income	(17)	¥ (4)
Other (income) and expense \| Interest rate swap agreements
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in income	4
Other (income) and expense \| Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in income	¥ 0

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.

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+ Details