v3.25.2
Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair value, measurements, recurring [Member] - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Disclosure details of fair value measurements of financial assets [Line items]    
Balance at beginning of year ¥ 432,259 ¥ 400,606
Net income (loss) (62,873) 22,282
Other comprehensive income (loss) (40,717) (6,803)
Purchases and issuances 45,902 32,678
Sales and settlements (10,245) (7,126)
Transfer to (from) Level 3 (81,009) 21
Others 9,939 (9,399)
Balance at end of year 293,257 432,259
Unrealized gains or losses included in profit or loss on assets held at March 31 (87,741) 22,214
Total (87,741) 22,214
Public and corporate bonds [Member]    
Disclosure details of fair value measurements of financial assets [Line items]    
Balance at beginning of year 31,170 33,332
Net income (loss) (8) 28
Purchases and issuances 9,572 4,910
Sales and settlements (9,210) (6,155)
Transfer to (from) Level 3 (3,125) 21
Others 1,711 (967)
Balance at end of year 30,111 31,170
Unrealized gains or losses included in profit or loss on assets held at March 31 (76) (40)
Total (76) (40)
Stocks [Member]    
Disclosure details of fair value measurements of financial assets [Line items]    
Balance at beginning of year 401,089 367,274
Net income (loss) (87,665) 22,254
Other comprehensive income (loss) (40,717) (6,803)
Purchases and issuances 36,330 27,768
Sales and settlements (1,035) (971)
Transfer to (from) Level 3 (77,884)  
Others 8,228 (8,432)
Balance at end of year 238,346 401,089
Unrealized gains or losses included in profit or loss on assets held at March 31 (87,665) 22,254
Total (87,665) ¥ 22,254
Derivative financial instruments [Member]    
Disclosure details of fair value measurements of financial assets [Line items]    
Net income (loss) 24,800  
Balance at end of year ¥ 24,800