Credit Quality of Financial Assets and the Allowance for Credit Losses - Summary of Financial Effect of Modifications of Financing Receivable (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
Sep. 30, 2026	Sep. 30, 2025
Interest rate reduction \| Consumer borrowers \| Other \| Maximum
Financing Receivable, Modifications [Line Items]
Interest rate reduction	16.40%
Interest rate reduction \| Consumer borrowers \| Other \| Minimum
Financing Receivable, Modifications [Line Items]
Interest rate reduction	11.70%
Interest rate reduction \| Corporate borrowers \| Other than non-recourse loans \| Commercial, industrial and other companies \| Overseas \| Maximum
Financing Receivable, Modifications [Line Items]
Interest rate reduction	9.70%	13.10%
Interest rate reduction \| Corporate borrowers \| Other than non-recourse loans \| Commercial, industrial and other companies \| Overseas \| Minimum
Financing Receivable, Modifications [Line Items]
Interest rate reduction	9.50%	3.30%
Term extension \| Consumer borrowers \| Other
Financing Receivable, Modifications [Line Items]
Term extension	10 months 24 days	1 year
Term extension \| Corporate borrowers \| Overseas
Financing Receivable, Modifications [Line Items]
Term extension	6 months
Term extension \| Corporate borrowers \| Other than non-recourse loans \| Real estate companies \| Japan
Financing Receivable, Modifications [Line Items]
Term extension	3 months 18 days	6 months
Term extension \| Corporate borrowers \| Other than non-recourse loans \| Commercial, industrial and other companies \| Japan
Financing Receivable, Modifications [Line Items]
Term extension		10 months 24 days
Term extension \| Corporate borrowers \| Other than non-recourse loans \| Commercial, industrial and other companies \| Overseas
Financing Receivable, Modifications [Line Items]
Term extension	2 years	6 months
Term extension \| Net investment in leases \| Japan
Financing Receivable, Modifications [Line Items]
Term extension	6 months	2 months 12 days
Principal forgiveness \| Consumer borrowers \| Real estate loans
Financing Receivable, Modifications [Line Items]
Principal forgiveness	¥ 36	¥ 54
Principal forgiveness \| Corporate borrowers \| Other than non-recourse loans \| Commercial, industrial and other companies \| Overseas
Financing Receivable, Modifications [Line Items]
Principal forgiveness	14	¥ 1,099
Principal forgiveness \| Net investment in leases \| Overseas
Financing Receivable, Modifications [Line Items]
Principal forgiveness	¥ 33

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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- Definition

Percentage of decrease in weighted-average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

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- Definition

Period of increase in weighted-average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- Definition

Amount of increase (decrease) in amortized cost of financing receivable modified for debtor experiencing financial difficulty.

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