v3.25.2
Insurance contracts in the financial services segment - Summary of Insurance revenue and the CSM by transition approach (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Disclosure In Tabular Form Of Insurance Revenue And Changes In Contractual Service Margin By Transition Approach [Line Items]    
Beginning balance ¥ 2,108,088 ¥ 2,052,617
Changes that relate to future service 101,865 149,241
Changes that relate to current service (151,025) (151,841)
Insurance finance expense (income) 30,155 57,995
Other (1,334) 76
Ending balance 2,087,749 2,108,088
Contracts measured under the modified retrospective approach at transition [member]    
Disclosure In Tabular Form Of Insurance Revenue And Changes In Contractual Service Margin By Transition Approach [Line Items]    
Beginning balance 763,669 864,530
Changes that relate to future service (89,828) (61,165)
Changes that relate to current service (55,642) (66,827)
Insurance finance expense (income) 23,501 26,954
Other (1,090) 177
Ending balance 640,610 763,669
Contracts measured under the fair value approach at transition [member]    
Disclosure In Tabular Form Of Insurance Revenue And Changes In Contractual Service Margin By Transition Approach [Line Items]    
Beginning balance 86,271 58,008
Changes that relate to future service 556 32,341
Changes that relate to current service (7,020) (5,834)
Insurance finance expense (income) 781 1,673
Other   83
Ending balance 80,588 86,271
New contracts and contracts measured under the full retrospective approach at transition [member]    
Disclosure In Tabular Form Of Insurance Revenue And Changes In Contractual Service Margin By Transition Approach [Line Items]    
Beginning balance 1,258,148 1,130,079
Changes that relate to future service 191,137 178,065
Changes that relate to current service (88,363) (79,180)
Insurance finance expense (income) 5,873 29,368
Other (244) (184)
Ending balance ¥ 1,366,551 ¥ 1,258,148