v3.26.1
Non-trading investments - Summary of AFS debt securities in an unrealized loss position (Detail)
¥ in Millions
Mar. 31, 2026
JPY (¥)
Securities
Mar. 31, 2025
JPY (¥)
Securities
Fair value    
Total ¥ 271,344 ¥ 94,656
Unrealized losses    
Total ¥ (4,908) ¥ (1,693)
Number of debt securities    
Total | Securities 195 79
Japanese government securities [Member]    
Fair value    
Less than 12 months ¥ 74,665 ¥ 24,814
12 months or longer 24,819  
Total 99,484 24,814
Unrealized losses    
Less than 12 months (311) (187)
12 months or longer (182)  
Total ¥ (493) ¥ (187)
Number of debt securities    
Less than 12 months | Securities 8 4
12 months or longer | Securities 4  
Total | Securities 12 4
Japanese agency and municipal securities [Member]    
Fair value    
Less than 12 months ¥ 89,242 ¥ 68,063
12 months or longer 67,268  
Total 156,510 68,063
Unrealized losses    
Less than 12 months (1,828) (1,495)
12 months or longer (2,301)  
Total ¥ (4,129) ¥ (1,495)
Number of debt securities    
Less than 12 months | Securities 80 72
12 months or longer | Securities 72  
Total | Securities 152 72
Bank and corporate debt securities [Member]    
Fair value    
Less than 12 months ¥ 13,485 ¥ 1,779
12 months or longer 1,865  
Total 15,350 1,779
Unrealized losses    
Less than 12 months (260) (11)
12 months or longer (26)  
Total ¥ (286) ¥ (11)
Number of debt securities    
Less than 12 months | Securities 28 3
12 months or longer | Securities 3  
Total | Securities 31 3