v3.26.3
Long-Duration Insurance Contracts Relating to Life Insurance Operations - Schedule of Deferred Policy Acquisition Costs (Detail) - JPY (¥)
¥ in Millions
6 Months Ended 12 Months Ended
Sep. 30, 2026
Mar. 31, 2026
Deferred Policy Acquisition Cost [Line Items]    
Beginning balance ¥ 332,892 ¥ 315,840
Capitalization 18,243 39,269
Amortization (11,031) (20,692)
Effect of changes in foreign exchange rate (1,253) 5,195
Others [1] (1,231) (6,720)
Ending balance 337,620 332,892
Yen-denominated insurance (First Sector)    
Deferred Policy Acquisition Cost [Line Items]    
Beginning balance 99,890 89,361
Capitalization 9,514 17,649
Amortization (3,921) (7,120)
Effect of changes in foreign exchange rate 0 0
Others [1] 0 0
Ending balance 105,483 99,890
Yen-denominated insurance (Third Sector)    
Deferred Policy Acquisition Cost [Line Items]    
Beginning balance 166,467 168,689
Capitalization 3,547 7,784
Amortization (4,963) (10,006)
Effect of changes in foreign exchange rate 0 0
Others [1] 0 0
Ending balance 165,051 166,467
Foreign currency denominated insurance    
Deferred Policy Acquisition Cost [Line Items]    
Beginning balance 64,915 57,151
Capitalization 3,057 6,504
Amortization (1,754) (3,018)
Effect of changes in foreign exchange rate (1,021) 4,278
Others [1] 0 0
Ending balance 65,197 64,915
Single- payment whole life insurance    
Deferred Policy Acquisition Cost [Line Items]    
Beginning balance 1,620 639
Capitalization 2,125 7,332
Amortization (393) (548)
Effect of changes in foreign exchange rate (232) 917
Others [1] (1,231) (6,720)
Ending balance ¥ 1,889 ¥ 1,620
[1] Others include adjustments of reinsurance.