Investments - Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity (Detail) - JPY (¥)
¥ in Millions |
Mar. 31, 2026 |
Mar. 31, 2025 |
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
¥ 15,842,720
|
|
| Due after one year through five years, amortized cost |
4,089,324
|
|
| Due after five years through ten years, amortized cost |
1,327,908
|
|
| Due after ten years, amortized cost |
711,775
|
|
| Total |
21,971,727
|
|
| Due in one year or less, amortized cost |
89,991
|
|
| Due after one year through five years, amortized cost |
119,941
|
|
| Due after five years through ten years, amortized cost |
209,636
|
|
| Due after ten years, amortized cost |
4,432,816
|
|
| Amortized cost, held-to-maturity securities |
4,852,384
|
¥ 4,185,763
|
| Due in one year or less, fair value |
15,832,983
|
|
| Due after one year through five years, fair value |
4,072,790
|
|
| Due after five years through ten years, fair value |
1,288,718
|
|
| Due after ten years, fair value |
654,197
|
|
| Total |
21,848,687
|
|
| Due in one year or less, fair value |
89,076
|
|
| Due after one year through five years, fair value |
115,131
|
|
| Due after five years through ten years, fair value |
189,006
|
|
| Due after ten years, fair value |
4,317,851
|
|
| Total |
4,711,064
|
|
| Debt securities | Japanese government bonds |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
12,024,349
|
|
| Due after one year through five years, amortized cost |
2,067,881
|
|
| Due after five years through ten years, amortized cost |
865,813
|
|
| Due after ten years, amortized cost |
19,784
|
|
| Total |
14,977,828
|
|
| Due in one year or less, amortized cost |
89,991
|
|
| Due after one year through five years, amortized cost |
119,941
|
|
| Due after five years through ten years, amortized cost |
209,636
|
|
| Due after ten years, amortized cost |
0
|
|
| Amortized cost, held-to-maturity securities |
419,568
|
|
| Due in one year or less, fair value |
12,014,919
|
|
| Due after one year through five years, fair value |
2,057,650
|
|
| Due after five years through ten years, fair value |
832,541
|
|
| Due after ten years, fair value |
19,810
|
|
| Total |
14,924,920
|
|
| Due in one year or less, fair value |
89,076
|
|
| Due after one year through five years, fair value |
115,131
|
|
| Due after five years through ten years, fair value |
189,006
|
|
| Due after ten years, fair value |
0
|
|
| Total |
393,213
|
|
| Debt securities | Japanese local government bonds |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
40,544
|
|
| Due after one year through five years, amortized cost |
65,219
|
|
| Due after five years through ten years, amortized cost |
51,513
|
|
| Due after ten years, amortized cost |
293
|
|
| Total |
157,569
|
|
| Due in one year or less, fair value |
40,375
|
|
| Due after one year through five years, fair value |
62,607
|
|
| Due after five years through ten years, fair value |
46,478
|
|
| Due after ten years, fair value |
241
|
|
| Total |
149,702
|
|
| Debt securities | U.S. Treasury bonds and federal agency securities |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
137,811
|
|
| Due after one year through five years, amortized cost |
0
|
|
| Due after five years through ten years, amortized cost |
0
|
|
| Due after ten years, amortized cost |
0
|
|
| Total |
137,811
|
|
| Due in one year or less, fair value |
137,973
|
|
| Due after one year through five years, fair value |
0
|
|
| Due after five years through ten years, fair value |
0
|
|
| Due after ten years, fair value |
0
|
|
| Total |
137,973
|
|
| Debt securities | Other foreign government bonds |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
2,933,330
|
|
| Due after one year through five years, amortized cost |
626,880
|
|
| Due after five years through ten years, amortized cost |
1,302
|
|
| Due after ten years, amortized cost |
1,297
|
|
| Total |
3,562,809
|
|
| Due in one year or less, fair value |
2,933,580
|
|
| Due after one year through five years, fair value |
627,779
|
|
| Due after five years through ten years, fair value |
1,302
|
|
| Due after ten years, fair value |
1,297
|
|
| Total |
3,563,958
|
|
| Debt securities | Agency mortgage-backed securities |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
0
|
|
| Due after one year through five years, amortized cost |
0
|
|
| Due after five years through ten years, amortized cost |
522
|
|
| Due after ten years, amortized cost |
342,221
|
|
| Total |
342,743
|
|
| Due in one year or less, amortized cost |
0
|
|
| Due after one year through five years, amortized cost |
0
|
|
| Due after five years through ten years, amortized cost |
0
|
|
| Due after ten years, amortized cost |
4,432,816
|
|
| Amortized cost, held-to-maturity securities |
4,432,816
|
|
| Due in one year or less, fair value |
0
|
|
| Due after one year through five years, fair value |
0
|
|
| Due after five years through ten years, fair value |
512
|
|
| Due after ten years, fair value |
281,323
|
|
| Total |
281,835
|
|
| Due in one year or less, fair value |
0
|
|
| Due after one year through five years, fair value |
0
|
|
| Due after five years through ten years, fair value |
0
|
|
| Due after ten years, fair value |
4,317,851
|
|
| Total |
4,317,851
|
|
| Debt securities | Residential mortgage-backed securities |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
127
|
|
| Due after one year through five years, amortized cost |
837
|
|
| Due after five years through ten years, amortized cost |
9,666
|
|
| Due after ten years, amortized cost |
1,164
|
|
| Total |
11,794
|
|
| Due in one year or less, fair value |
127
|
|
| Due after one year through five years, fair value |
837
|
|
| Due after five years through ten years, fair value |
9,666
|
|
| Due after ten years, fair value |
1,164
|
|
| Total |
11,794
|
|
| Debt securities | Commercial mortgage-backed securities |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
6,070
|
|
| Due after one year through five years, amortized cost |
659,622
|
|
| Due after five years through ten years, amortized cost |
246,150
|
|
| Due after ten years, amortized cost |
1,000
|
|
| Total |
912,841
|
|
| Due in one year or less, fair value |
6,080
|
|
| Due after one year through five years, fair value |
659,530
|
|
| Due after five years through ten years, fair value |
247,434
|
|
| Due after ten years, fair value |
967
|
|
| Total |
914,012
|
|
| Debt securities | Japanese corporate bonds and other debt securities |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
92,304
|
|
| Due after one year through five years, amortized cost |
356,607
|
|
| Due after five years through ten years, amortized cost |
131,633
|
|
| Due after ten years, amortized cost |
345,549
|
|
| Total |
926,093
|
|
| Due in one year or less, fair value |
91,873
|
|
| Due after one year through five years, fair value |
352,530
|
|
| Due after five years through ten years, fair value |
129,397
|
|
| Due after ten years, fair value |
348,928
|
|
| Total |
922,727
|
|
| Debt securities | Foreign corporate bonds and other debt securities |
|
|
| Investments Classified by Contractual Maturity Date [Line Items] |
|
|
| Due in one year or less, amortized cost |
608,186
|
|
| Due after one year through five years, amortized cost |
312,278
|
|
| Due after five years through ten years, amortized cost |
21,309
|
|
| Due after ten years, amortized cost |
466
|
|
| Total |
942,239
|
|
| Due in one year or less, fair value |
608,056
|
|
| Due after one year through five years, fair value |
311,856
|
|
| Due after five years through ten years, fair value |
21,388
|
|
| Due after ten years, fair value |
466
|
|
| Total |
¥ 941,766
|
|