v3.26.3
Long-Duration Insurance Contracts Relating to Life Insurance Operations - Schedule of Reconciliation of Liability For Future Policy Benefits (Detail) - JPY (¥)
¥ in Millions
6 Months Ended 12 Months Ended
Sep. 30, 2026
Mar. 31, 2026
Liability for Future Policy Benefit, Activity [Line Items]    
The liability for future policy benefits, after reinsurance recoverable ¥ 1,265,430 ¥ 1,277,462
Yen-denominated insurance (First Sector)    
Liability for Future Policy Benefit, Activity [Line Items]    
Balance at beginning of year 803,396 855,431
Beginning balance at original discount rate 865,378 877,300
Effect of changes in cash flow assumptions 0 (19,239)
Effect of actual variances from expected experience 3,993 871
Adjusted beginning balance 869,371 858,932
Issuances 58,486 127,215
Interests 5,958 11,351
Net premium earned (59,384) (127,464)
Actual variances from cash flow assumptions 0 (936)
Derecognition 0 (3,720)
Effect of changes in foreign exchange rate 0 0
Ending balance at original discount rate 874,431 865,378
Effect of changes in discount rates (78,316) (61,982)
Ending balance 796,115 803,396
Balances at beginning of year 1,370,583 1,511,436
Beginning balance at original discount rate 1,819,619 1,750,912
Effect of changes in cash flow assumptions 0 (20,056)
Effect of actual variances from expected experience 4,330 0
Adjusted beginning balances 1,823,949 1,730,856
Issuances 58,486 127,215
Interests 13,810 26,152
Insurance claims paid (33,598) (61,802)
Actual variances from cash flow assumptions 0 (9,699)
Derecognition 0 6,897
Effect of changes in foreign exchange rate 0 0
Ending balance at original discount rate 1,862,647 1,819,619
Effect of changes in discount rates (512,198) (449,036)
Ending balance 1,350,449 1,370,583
Net liability for future policy benefits 554,334 567,187
Deferred profit liabilities 82,474 74,053
Subtotal 636,808 641,240
Less: Reinsurance recoverable 82 162
The liability for future policy benefits, after reinsurance recoverable 636,726 641,078
Yen-denominated insurance (Third Sector)    
Liability for Future Policy Benefit, Activity [Line Items]    
Balance at beginning of year 999,049 1,162,214
Beginning balance at original discount rate 1,134,618 1,216,705
Effect of changes in cash flow assumptions 0 (18,434)
Effect of actual variances from expected experience 9,758 4,687
Adjusted beginning balance 1,144,376 1,202,958
Issuances 8,337 24,195
Interests 8,131 16,684
Net premium earned (55,574) (113,506)
Actual variances from cash flow assumptions 0 (665)
Derecognition 0 4,952
Effect of changes in foreign exchange rate 0 0
Ending balance at original discount rate 1,105,270 1,134,618
Effect of changes in discount rates (165,515) (135,569)
Ending balance 939,755 999,049
Balances at beginning of year 1,344,482 1,659,960
Beginning balance at original discount rate 1,872,456 1,878,075
Effect of changes in cash flow assumptions 0 5,429
Effect of actual variances from expected experience 11,819 0
Adjusted beginning balances 1,884,275 1,883,504
Issuances 8,337 24,195
Interests 14,322 28,183
Insurance claims paid (39,273) (77,181)
Actual variances from cash flow assumptions 0 (2,030)
Derecognition 0 15,785
Effect of changes in foreign exchange rate 0 0
Ending balance at original discount rate 1,867,661 1,872,456
Effect of changes in discount rates (598,289) (527,974)
Ending balance 1,269,372 1,344,482
Net liability for future policy benefits 329,617 345,433
Deferred profit liabilities 67,396 66,559
Subtotal 397,013 411,992
Less: Reinsurance recoverable 0 0
The liability for future policy benefits, after reinsurance recoverable 397,013 411,992
Foreign currency denominated insurance    
Liability for Future Policy Benefit, Activity [Line Items]    
Balance at beginning of year 323,615 345,932
Beginning balance at original discount rate 339,085 368,846
Effect of changes in cash flow assumptions 0 (17,187)
Effect of actual variances from expected experience (6,024) (1,017)
Adjusted beginning balance 333,061 350,642
Issuances 12,301 29,171
Interests 5,308 11,058
Net premium earned (36,139) (63,084)
Actual variances from cash flow assumptions 0 (589)
Derecognition 0 (10,539)
Effect of changes in foreign exchange rate (5,217) 22,426
Ending balance at original discount rate 309,314 339,085
Effect of changes in discount rates (21,950) (15,470)
Ending balance 287,364 323,615
Balances at beginning of year 495,324 442,939
Beginning balance at original discount rate 696,679 650,005
Effect of changes in cash flow assumptions 0 (20,141)
Effect of actual variances from expected experience (6,416) 0
Adjusted beginning balances 690,263 629,864
Issuances 12,301 29,171
Interests 10,629 19,736
Insurance claims paid (9,101) (14,131)
Actual variances from cash flow assumptions 0 6,037
Derecognition 0 (19,310)
Effect of changes in foreign exchange rate (11,185) 45,312
Ending balance at original discount rate 692,907 696,679
Effect of changes in discount rates (233,717) (201,355)
Ending balance 459,190 495,324
Net liability for future policy benefits 171,826 171,709
Deferred profit liabilities 59,865 52,683
Subtotal 231,691 224,392
Less: Reinsurance recoverable 0 0
The liability for future policy benefits, after reinsurance recoverable ¥ 231,691 ¥ 224,392