v3.25.2
Insurance contracts in the financial services segment - Summary of Changing the Underlying Assumptions of MCEV (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2023
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes ¥ 1,473,726 ¥ 1,268,662 ¥ 1,274,496
Equity 8,510,151 7,756,105 ¥ 6,657,150
Interest rates, measurement input [member] | 50bp decrease [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 2,418 12,949  
Equity 130,997 153,000  
Interest rates, measurement input [member] | 50bp decrease [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (96,388) (152,232)  
Equity (489,064) (653,432)  
Interest rates, measurement input [member] | 50bp decrease [member] | Financial instruments [Member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 98,806 165,181  
Equity 620,061 806,432  
Interest rates, measurement input [member] | 50bp increase [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (18,124) (30,632)  
Equity (132,719) (156,740)  
Interest rates, measurement input [member] | 50bp increase [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 69,393 112,418  
Equity 413,835 548,289  
Interest rates, measurement input [member] | 50bp increase [member] | Financial instruments [Member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (87,517) (143,050)  
Equity (546,554) (705,029)  
Fair value of stocks [Member] | 10% decrease [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (8,212) (2,362)  
Equity (6,266) (2,161)  
Fair value of stocks [Member] | 10% decrease [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 404,020 339,421  
Equity 290,894 244,383  
Fair value of stocks [Member] | 10% decrease [member] | Financial instruments [Member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (412,232) (341,783)  
Equity (297,160) (246,544)  
Fair value of stocks [Member] | 10% increase [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 4,420 (3,138)  
Equity 3,535 (1,799)  
Fair value of stocks [Member] | 10% increase [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (407,812) (344,921)  
Equity (293,625) (248,343)  
Fair value of stocks [Member] | 10% increase [member] | Financial instruments [Member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 412,232 341,783  
Equity 297,160 246,544  
Foreign exchange rates [Member] | 10% appreciation of the Yen [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (7,381) (1,601)  
Equity 27,654 27,485  
Foreign exchange rates [Member] | 10% appreciation of the Yen [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 539,518 468,851  
Equity 366,832 315,357  
Foreign exchange rates [Member] | 10% appreciation of the Yen [member] | Financial instruments [Member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (546,899) (470,452)  
Equity (339,178) (287,872)  
Foreign exchange rates [Member] | 10% depreciation of the Yen [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 3,744 (5,037)  
Equity (30,272) (32,264)  
Foreign exchange rates [Member] | 10% depreciation of the Yen [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (543,155) (475,489)  
Equity (369,450) (320,136)  
Foreign exchange rates [Member] | 10% depreciation of the Yen [member] | Financial instruments [Member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 546,899 470,452  
Equity 339,178 287,872  
Maintenance expenses rates [Member] | 10% increase [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (4,313) (4,780)  
Equity (5,390) (8,024)  
Maintenance expenses rates [Member] | 10% increase [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (4,313) (4,780)  
Equity (5,390) (8,024)  
Lapse and surrender rates [Member] | 10% increase [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (23,254) (13,351)  
Equity (34,971) (13,140)  
Lapse and surrender rates [Member] | 10% increase [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (23,254) (13,351)  
Equity (34,971) (13,140)  
Mortality rates (death protection) [Member] | 5% increase [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (4,838) (4,892)  
Equity (4,710) (5,501)  
Mortality rates (death protection) [Member] | 5% increase [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (4,838) (4,892)  
Equity (4,710) (5,501)  
Mortality rates (third sector / annuity products) [Member] | 5% increase [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 960 1,382  
Equity (467) 2,054  
Mortality rates (third sector / annuity products) [Member] | 5% increase [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes 960 1,382  
Equity (467) 2,054  
Morbidity rates [Member] | 5% increase [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (7,191) (8,239)  
Equity (4,639) (11,700)  
Morbidity rates [Member] | 5% increase [member] | Insurance contracts [member]      
Disclosure Of Changes in Underlying Assumptions Of Market Consistent Embedded value [Line Items]      
Income before income taxes (7,191) (8,239)  
Equity ¥ (4,639) ¥ (11,700)