v3.26.3
Significant Accounting and Reporting Policies - Additional Information (Detail) - JPY (¥)
¥ in Millions
6 Months Ended 12 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Mar. 31, 2026
Significant Accounting Policies [Line Items]      
A maximum lag period of recognizing the results of subsidiaries and affiliates 3 months    
Residential condominiums under development ¥ 147,783   ¥ 140,800
Finished goods ¥ 132,454   128,387
Effective tax rate 30.90% 29.70%  
Statutory income tax rate 32.30% 31.50%  
Loans held for sale in installment loans ¥ 198,591   105,720
Goodwill acquired 750,078   773,592
Other intangible assets 552,966   570,683
Aggregate loan fair value 60,859   78,020
Accumulated depreciation of Investment in operating leases 1,053,279   1,033,293
Revision of Prior Period, Adjustment      
Significant Accounting Policies [Line Items]      
Goodwill acquired     773,592
Property under Facility Operations      
Significant Accounting Policies [Line Items]      
Accumulated depreciation 267,723   245,328
Office Facilities      
Significant Accounting Policies [Line Items]      
Accumulated depreciation ¥ 65,812   ¥ 69,281
Minimum      
Significant Accounting Policies [Line Items]      
Income tax settlement by tax authority 50.00%    
Minimum | Investment in Corporate Entities      
Significant Accounting Policies [Line Items]      
Equity method investment, ownership percentage 20.00%    
Minimum | Investments in Partnerships and Other Investments      
Significant Accounting Policies [Line Items]      
Equity method investment, ownership percentage 3.00%    
Maximum | Investment in Corporate Entities      
Significant Accounting Policies [Line Items]      
Equity method investment, ownership percentage 50.00%    
Maximum | Investments in Partnerships and Other Investments      
Significant Accounting Policies [Line Items]      
Equity method investment, ownership percentage 5.00%