v3.26.1
Financial Risk Management - Maturity Analysis of Contractual Undiscounted Cash Flows for Financial Liabilities (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments ¥ 395,978,569 ¥ 372,504,746
Contractual undiscounted cash flows, Derivative financial instruments 11,472,444 9,303,258
On demand [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 247,524,538 236,220,113
Contractual undiscounted cash flows, Derivative financial instruments 11,090,691 8,882,734
Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 97,427,902 89,749,623
Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 29,063,297 23,059,702
Contractual undiscounted cash flows, Derivative financial instruments 17,698 20,073
Later than one year and not later than three years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 9,178,570 11,807,835
Contractual undiscounted cash flows, Derivative financial instruments 51,341 75,619
Later than three years and not later than five years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 5,618,661 4,363,807
Contractual undiscounted cash flows, Derivative financial instruments 142,860 122,772
Later than five years [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 7,165,601 7,303,666
Contractual undiscounted cash flows, Derivative financial instruments 169,854 202,060
Deposits from customers [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 201,971,885 190,043,600
Deposits from customers [Member] | On demand [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 122,293,981 121,012,519
Deposits from customers [Member] | Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 52,209,492 46,594,286
Deposits from customers [Member] | Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 22,416,618 17,173,432
Deposits from customers [Member] | Later than one year and not later than three years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 2,799,727 3,157,803
Deposits from customers [Member] | Later than three years and not later than five years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 1,100,716 1,006,617
Deposits from customers [Member] | Later than five years [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 1,151,351 1,098,943
Call money and bills sold [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 3,656,737 4,378,277
Call money and bills sold [Member] | Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 3,629,571 4,346,342
Call money and bills sold [Member] | Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 27,166 31,935
Repurchase agreements and cash collateral on securities lent [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 24,176,556 27,791,101
Repurchase agreements and cash collateral on securities lent [Member] | On demand [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 278,146 155,438
Repurchase agreements and cash collateral on securities lent [Member] | Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 23,472,367 27,456,024
Repurchase agreements and cash collateral on securities lent [Member] | Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 426,043 179,639
Financial liabilities at fair value through profit or loss that meet definition of held for trading, category [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 4,130,591 4,838,439
Financial liabilities at fair value through profit or loss that meet definition of held for trading, category [member] | On demand [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 4,130,591 4,838,439
Financial liabilities designated at fair value through profit or loss [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 734,491 643,610
Financial liabilities designated at fair value through profit or loss [member] | Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 19,391 3,100
Financial liabilities designated at fair value through profit or loss [member] | Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 59,459 41,121
Financial liabilities designated at fair value through profit or loss [member] | Later than one year and not later than three years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 91,540 101,704
Financial liabilities designated at fair value through profit or loss [member] | Later than three years and not later than five years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 108,011 79,461
Financial liabilities designated at fair value through profit or loss [member] | Later than five years [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 456,090 418,224
Borrowings [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 10,203,381 12,324,741
Borrowings [Member] | On demand [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 280,644 301,721
Borrowings [Member] | Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 1,203,233 1,102,473
Borrowings [Member] | Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 3,356,156 3,184,919
Borrowings [Member] | Later than one year and not later than three years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 3,446,820 5,090,260
Borrowings [Member] | Later than three years and not later than five years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 606,363 530,156
Borrowings [Member] | Later than five years [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 1,310,165 2,115,212
Debt securities in issue [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 16,930,700 14,761,931
Debt securities in issue [Member] | Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 3,661,830 2,858,867
Debt securities in issue [Member] | Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 2,708,049 2,381,446
Debt securities in issue [Member] | Later than one year and not later than three years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 2,726,254 3,342,775
Debt securities in issue [Member] | Later than three years and not later than five years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 3,733,556 2,675,596
Debt securities in issue [Member] | Later than five years [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 4,101,011 3,503,247
Lease payable [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 401,696 426,087
Lease payable [Member] | Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 19,250 19,100
Lease payable [Member] | Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 60,970 62,448
Lease payable [Member] | Later than one year and not later than three years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 114,229 115,293
Lease payable [Member] | Later than three years and not later than five years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 69,869 71,831
Lease payable [Member] | Later than five years [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 137,378 157,415
Others-liabilities [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 16,425,020 10,346,934
Others-liabilities [member] | On demand [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 3,193,664 2,961,970
Others-liabilities [member] | Not later than three months [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 13,212,768 7,369,431
Others-liabilities [member] | Later than three months and not later than one year [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 8,836 4,762
Others-liabilities [member] | Later than three years and not later than five years [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 146 146
Others-liabilities [member] | Later than five years [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 9,606 10,625
Loan commitments [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 100,314,339 91,810,227
Loan commitments [member] | On demand [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 100,314,339 91,810,227
Financial guarantees and other credit-related contingent liabilities [member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments 17,033,173 15,139,799
Financial guarantees and other credit-related contingent liabilities [member] | On demand [Member]    
Non-derivative financial instruments:    
Contractual undiscounted cash flows, Non-derivative financial instruments ¥ 17,033,173 ¥ 15,139,799