v3.26.1
Long-Duration Insurance Contracts Relating to Life Insurance Operations - Schedule of Reconciliation of Liability For Future Policy Benefits (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Liability for Future Policy Benefit, Activity [Line Items]    
The liability for future policy benefits, after reinsurance recoverable ¥ 1,277,462 ¥ 1,424,312
Yen-denominated insurance (First Sector)    
Liability for Future Policy Benefit, Activity [Line Items]    
Balance at beginning of year 855,431 873,038
Beginning balance at original discount rate 877,300 858,959
Effect of changes in cash flow assumptions (19,239) (9,660)
Effect of actual variances from expected experience 871 984
Adjusted beginning balance 858,932 850,283
Issuances 127,215 130,605
Interests 11,351 10,568
Net premium earned (127,464) (116,850)
Actual variances from cash flow assumptions (936) (437)
Derecognition (3,720) 3,131
Effect of changes in foreign exchange rate 0 0
Ending balance at original discount rate 865,378 877,300
Effect of changes in discount rates (61,982) (21,869)
Ending balance 803,396 855,431
Balances at beginning of year 1,511,436 1,565,877
Beginning balance at original discount rate 1,750,912 1,658,143
Effect of changes in cash flow assumptions (20,056) (10,284)
Adjusted beginning balances 1,730,856 1,647,859
Issuances 127,215 130,605
Interests 26,152 24,463
Insurance claims paid (61,802) (57,099)
Actual variances from cash flow assumptions (9,699) (9,571)
Derecognition 6,897 14,655
Effect of changes in foreign exchange rate 0 0
Ending balance at original discount rate 1,819,619 1,750,912
Effect of changes in discount rates (449,036) (239,476)
Ending balance 1,370,583 1,511,436
Net liability for future policy benefits 567,187 656,005
Deferred profit liabilities 74,053 61,448
Subtotal 641,240 717,453
Less: Reinsurance recoverable 162 196
The liability for future policy benefits, after reinsurance recoverable 641,078 717,257
Yen-denominated insurance (Third Sector)    
Liability for Future Policy Benefit, Activity [Line Items]    
Balance at beginning of year 1,162,214 1,306,719
Beginning balance at original discount rate 1,216,705 1,289,145
Effect of changes in cash flow assumptions (18,434) (7,648)
Effect of actual variances from expected experience 4,687 812
Adjusted beginning balance 1,202,958 1,282,309
Issuances 24,195 34,189
Interests 16,684 17,489
Net premium earned (113,506) (116,049)
Actual variances from cash flow assumptions (665) (770)
Derecognition 4,952 (463)
Effect of changes in foreign exchange rate 0 0
Ending balance at original discount rate 1,134,618 1,216,705
Effect of changes in discount rates (135,569) (54,491)
Ending balance 999,049 1,162,214
Balances at beginning of year 1,659,960 1,844,599
Beginning balance at original discount rate 1,878,075 1,895,730
Effect of changes in cash flow assumptions 5,429 (8,470)
Adjusted beginning balances 1,883,504 1,887,260
Issuances 24,195 34,189
Interests 28,183 27,997
Insurance claims paid (77,181) (72,044)
Actual variances from cash flow assumptions (2,030) (8,287)
Derecognition 15,785 8,960
Effect of changes in foreign exchange rate 0 0
Ending balance at original discount rate 1,872,456 1,878,075
Effect of changes in discount rates (527,974) (218,115)
Ending balance 1,344,482 1,659,960
Net liability for future policy benefits 345,433 497,746
Deferred profit liabilities 66,559 74,962
Subtotal 411,992 572,708
Less: Reinsurance recoverable 0 0
The liability for future policy benefits, after reinsurance recoverable 411,992 572,708
Foreign currency denominated insurance    
Liability for Future Policy Benefit, Activity [Line Items]    
Balance at beginning of year 345,932 389,664
Beginning balance at original discount rate 368,846 424,186
Effect of changes in cash flow assumptions (17,187) 66
Effect of actual variances from expected experience (1,017) (3,193)
Adjusted beginning balance 350,642 421,059
Issuances 29,171 31,717
Interests 11,058 12,323
Net premium earned (63,084) (62,788)
Actual variances from cash flow assumptions (589) (1,231)
Derecognition (10,539) (27,567)
Effect of changes in foreign exchange rate 22,426 (4,667)
Ending balance at original discount rate 339,085 368,846
Effect of changes in discount rates (15,470) (22,914)
Ending balance 323,615 345,932
Balances at beginning of year 442,939 447,081
Beginning balance at original discount rate 650,005 659,217
Effect of changes in cash flow assumptions (20,141) 81
Adjusted beginning balances 629,864 659,298
Issuances 29,171 31,717
Interests 19,736 19,385
Insurance claims paid (14,131) (18,634)
Actual variances from cash flow assumptions 6,037 13,086
Derecognition (19,310) (46,693)
Effect of changes in foreign exchange rate 45,312 (8,154)
Ending balance at original discount rate 696,679 650,005
Effect of changes in discount rates (201,355) (207,066)
Ending balance 495,324 442,939
Net liability for future policy benefits 171,709 97,007
Deferred profit liabilities 52,683 37,340
Subtotal 224,392 134,347
Less: Reinsurance recoverable 0 0
The liability for future policy benefits, after reinsurance recoverable ¥ 224,392 ¥ 134,347