Fair Value Measurements (Recorded Amounts of Major Assets Measured at Fair Value on Nonrecurring Basis) (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2025	Mar. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	¥ 85,724	¥ 97,694
Investment in Operating Leases	2,086,405	1,967,178
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	168
Real estate collateral-dependent loans (net of allowance for credit losses)	3,490	5,881
Investment in Operating Leases	234
Investment in operating leases, property under facility operations and office facilities		8,105
Certain equity securities	37,465	15,193
Certain equity method investments	1,109	20,619
Total	42,466	49,798
Fair Value, Measurements, Nonrecurring \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0
Real estate collateral-dependent loans (net of allowance for credit losses)	0	0
Investment in Operating Leases	0
Investment in operating leases, property under facility operations and office facilities		0
Certain equity securities	0	0
Certain equity method investments	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	47
Real estate collateral-dependent loans (net of allowance for credit losses)	0	0
Investment in Operating Leases	0
Investment in operating leases, property under facility operations and office facilities		0
Certain equity securities	37,465	15,193
Certain equity method investments	0	0
Total	37,512	15,193
Fair Value, Measurements, Nonrecurring \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	121
Real estate collateral-dependent loans (net of allowance for credit losses)	3,490	5,881
Investment in Operating Leases	234
Investment in operating leases, property under facility operations and office facilities		8,105
Certain equity securities	0	0
Certain equity method investments	1,109	20,619
Total	¥ 4,954	¥ 34,605

Investment In Operating Leases.

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Investment in operating leases, property under facility operations and office facilities.

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Real estate collateral-dependent loans (net allowance probable loan losses).

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Fair value portion of asset recognized for present right to economic benefit.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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