v3.25.2
Investment Securities (Investments by Length and Category in Continuous Loss Position) (Detail)
¥ in Millions
Mar. 31, 2025
JPY (¥)
security
Mar. 31, 2024
JPY (¥)
security
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 21,214,098 ¥ 19,994,182
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 123,701 20,779
Available-for-sale debt securities, Fair value, 12 months or more 3,762,645 5,230,206
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 217,766 259,469
Available-for-sale debt securities, Fair value, Total 24,976,743 25,224,388
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 341,467 ¥ 280,248
Available-for-sale debt securities, Number of securities | security 1,288 1,507
Japanese national government and Japanese government agency bonds    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 19,809,049 ¥ 18,640,364
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 109,736 9,427
Available-for-sale debt securities, Fair value, 12 months or more 1,160,183 1,756,792
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 122,881 116,671
Available-for-sale debt securities, Fair value, Total 20,969,232 20,397,156
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 232,617 ¥ 126,098
Available-for-sale debt securities, Number of securities | security 311 440
Japanese prefectural and municipal bonds    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 30,167 ¥ 416,047
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 82 1,502
Available-for-sale debt securities, Fair value, 12 months or more 279,731 520,133
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 9,697 8,298
Available-for-sale debt securities, Fair value, Total 309,898 936,180
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 9,779 ¥ 9,800
Available-for-sale debt securities, Number of securities | security 282 574
Foreign government and official institution bonds    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 710,517 ¥ 358,973
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 9,198 9,306
Available-for-sale debt securities, Fair value, 12 months or more 1,584,560 1,942,369
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 73,430 121,323
Available-for-sale debt securities, Fair value, Total 2,295,077 2,301,342
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 82,628 ¥ 130,629
Available-for-sale debt securities, Number of securities | security 104 97
Corporate bonds    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 206,591 ¥ 167,004
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 3,069 467
Available-for-sale debt securities, Fair value, 12 months or more 413,226 442,274
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 8,455 3,582
Available-for-sale debt securities, Fair value, Total 619,817 609,278
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 11,524 ¥ 4,049
Available-for-sale debt securities, Number of securities | security 483 309
Residential mortgage-backed securities    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 0 ¥ 185,197
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 0 14
Available-for-sale debt securities, Fair value, 12 months or more 274,894 343,621
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 211 331
Available-for-sale debt securities, Fair value, Total 274,894 528,818
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 211 ¥ 345
Available-for-sale debt securities, Number of securities | security 9 14
Asset-backed securities    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 244,037 ¥ 23,810
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 1,193 9
Available-for-sale debt securities, Fair value, 12 months or more 1,252 160,109
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 6 1,868
Available-for-sale debt securities, Fair value, Total 245,289 183,919
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 1,199 ¥ 1,877
Available-for-sale debt securities, Number of securities | security 25 17
Other debt securities    
Investment Securities [Line Items]    
Available-for-sale debt securities, Fair value, Less than 12 months ¥ 213,737 ¥ 202,787
Available-for-sale debt securities, Gross unrealized losses, Less than 12 months 423 54
Available-for-sale debt securities, Fair value, 12 months or more 48,799 64,908
Available-for-sale debt securities, Gross unrealized losses, 12 months or more 3,086 7,396
Available-for-sale debt securities, Fair value, Total 262,536 267,695
Available-for-sale debt securities, Gross unrealized losses, Total ¥ 3,509 ¥ 7,450
Available-for-sale debt securities, Number of securities | security 74 56