v3.26.1
Investment Securities (Investments by Length and Category in Continuous Loss Position) (Detail)
¥ in Millions
Mar. 31, 2026
JPY (¥)
security
Mar. 31, 2025
JPY (¥)
security
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 13,205,503 ¥ 21,214,098
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 34,559 123,701
Available-for-sale debt securities, Fair value, 12 months or more 3,746,768 3,762,645
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 321,427 217,766
Available-for-sale debt securities, Fair value, Total 16,952,271 24,976,743
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 355,986 ¥ 341,467
Available-for-sale debt securities, Number of securities | security 1,109 1,288
Japanese national government and Japanese government agency bonds    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 11,646,480 ¥ 19,809,049
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 22,273 109,736
Available-for-sale debt securities, Fair value, 12 months or more 1,671,333 1,160,183
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 241,280 122,881
Available-for-sale debt securities, Fair value, Total 13,317,813 20,969,232
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 263,553 ¥ 232,617
Available-for-sale debt securities, Number of securities | security 252 311
Japanese prefectural and municipal bonds    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 0 ¥ 30,167
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 0 82
Available-for-sale debt securities, Fair value, 12 months or more 166,380 279,731
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 10,587 9,697
Available-for-sale debt securities, Fair value, Total 166,380 309,898
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 10,587 ¥ 9,779
Available-for-sale debt securities, Number of securities | security 202 282
Foreign government and official institution bonds    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 1,128,963 ¥ 710,517
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 8,090 9,198
Available-for-sale debt securities, Fair value, 12 months or more 1,271,358 1,584,560
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 53,379 73,430
Available-for-sale debt securities, Fair value, Total 2,400,321 2,295,077
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 61,469 ¥ 82,628
Available-for-sale debt securities, Number of securities | security 105 104
Corporate bonds    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 203,323 ¥ 206,591
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 3,914 3,069
Available-for-sale debt securities, Fair value, 12 months or more 456,324 413,226
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 14,055 8,455
Available-for-sale debt securities, Fair value, Total 659,647 619,817
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 17,969 ¥ 11,524
Available-for-sale debt securities, Number of securities | security 479 483
Residential mortgage-backed securities    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 0 ¥ 0
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 0 0
Available-for-sale debt securities, Fair value, 12 months or more 113,974 274,894
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 109 211
Available-for-sale debt securities, Fair value, Total 113,974 274,894
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 109 ¥ 211
Available-for-sale debt securities, Number of securities | security 5 9
Asset-backed securities    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 55,271 ¥ 244,037
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 212 1,193
Available-for-sale debt securities, Fair value, 12 months or more 9,509 1,252
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 42 6
Available-for-sale debt securities, Fair value, Total 64,780 245,289
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 254 ¥ 1,199
Available-for-sale debt securities, Number of securities | security 14 25
Other debt securities    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 171,466 ¥ 213,737
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 70 423
Available-for-sale debt securities, Fair value, 12 months or more 57,890 48,799
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 1,975 3,086
Available-for-sale debt securities, Fair value, Total 229,356 262,536
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 2,045 ¥ 3,509
Available-for-sale debt securities, Number of securities | security 52 74