v3.26.1
Investment Securities - Schedule of Equity Instruments at Fair Value through Other Comprehensive Income (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Disclosure of detailed information about financial instruments [line items]    
Equity instruments at fair value through other comprehensive income ¥ 5,505,439 ¥ 5,170,856
Listed [member]    
Disclosure of detailed information about financial instruments [line items]    
Equity instruments at fair value through other comprehensive income 4,013,893 3,745,559
Unlisted [member]    
Disclosure of detailed information about financial instruments [line items]    
Equity instruments at fair value through other comprehensive income ¥ 1,491,546 ¥ 1,425,297