v3.26.1
Fair Value - Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Disclosure of fair value measurement of assets [line items]    
Beginning balance ¥ 1,081,937  
Ending balance 1,508,493 ¥ 1,081,937
Debt securities [member]    
Disclosure of fair value measurement of assets [line items]    
Beginning balance 84,018  
Ending balance 41,564 84,018
Measured at fair value on a recurring basis [member]    
Disclosure of fair value measurement of assets [line items]    
Beginning balance 736,745  
Ending balance 1,040,414 736,745
Measured at fair value on a recurring basis [member] | Level 3 [member]    
Disclosure of fair value measurement of assets [line items]    
Beginning balance 65,618  
Ending balance 86,340 65,618
Measured at fair value on a recurring basis [member] | Level 3 [member] | Derivatives [member]    
Disclosure of fair value measurement of assets [line items]    
Beginning balance 10,949 5,806
Profit or loss 302 5,339
Other comprehensive income
Purchases
Sales
Transfer to level 1 due to listing
Exchange differences on translating foreign operations 703 (196)
Other
Ending balance 11,954 10,949
Unrealized gains or losses included in profit or loss on assets held 302 5,339
Measured at fair value on a recurring basis [member] | Level 3 [member] | Debt securities [member]    
Disclosure of fair value measurement of assets [line items]    
Beginning balance 4,486 4,542
Profit or loss (153)
Other comprehensive income
Purchases
Sales
Transfer to level 1 due to listing
Exchange differences on translating foreign operations 310 97
Other
Ending balance 4,796 4,486
Unrealized gains or losses included in profit or loss on assets held (153)
Measured at fair value on a recurring basis [member] | Level 3 [member] | Equity securities [member]    
Disclosure of fair value measurement of assets [line items]    
Beginning balance 50,183 115,214
Profit or loss
Other comprehensive income 6,152 29,617
Purchases 11,221 3,304
Sales (662) (96,232)
Transfer to level 1 due to listing (15)
Exchange differences on translating foreign operations 1,564 (171)
Other 1,132 (1,534)
Ending balance 69,590 50,183
Unrealized gains or losses included in profit or loss on assets held