v3.26.3
Long-Duration Insurance Contracts Relating to Life Insurance Operations - Schedule of Liability For Future Policy Benefit Expected Future Policy Benefit Undiscounted Before Reinsurance (Detail) - JPY (¥)
¥ in Millions
Sep. 30, 2026
Mar. 31, 2026
Yen-denominated insurance (First Sector)    
Liability for Future Policy Benefit, Activity [Line Items]    
Expected future gross premiums - Undiscounted ¥ 1,606,031 ¥ 1,567,367
Expected future policy benefits and expenses - Undiscounted 2,741,666 2,621,312
Expected future gross premiums - Discounted 1,296,237 1,297,608
Expected future policy benefits and expenses - Discounted 1,350,449 1,370,583
Yen-denominated insurance (Third Sector)    
Liability for Future Policy Benefit, Activity [Line Items]    
Expected future gross premiums - Undiscounted 2,234,406 2,293,632
Expected future policy benefits and expenses - Undiscounted 2,632,828 2,637,437
Expected future gross premiums - Discounted 1,607,992 1,713,873
Expected future policy benefits and expenses - Discounted 1,269,372 1,344,482
Foreign currency denominated insurance    
Liability for Future Policy Benefit, Activity [Line Items]    
Expected future gross premiums - Undiscounted 540,604 583,537
Expected future policy benefits and expenses - Undiscounted 1,330,038 1,340,021
Expected future gross premiums - Discounted 431,026 478,421
Expected future policy benefits and expenses - Discounted ¥ 459,190 ¥ 495,324