v3.26.1
Repurchase Agreements, and Securities Lending Transactions Accounted for as Secured Borrowings (Gross Obligations by Remaining Contractual Maturity and Class of Collateral Pledged) (Detail) - JPY (¥)
¥ in Billions
Mar. 31, 2026
Mar. 31, 2025
Repurchase Agreements, and Securities Lending Transactions Accounted for as Secured Borrowings [Line Items]    
Payables under repurchase agreements ¥ 42,292 ¥ 46,381
Payables under securities lending transactions 1,252 737
Obligations to return securities received as collateral 8,468 6,047
Total 52,012 53,165
Overnight and open    
Repurchase Agreements, and Securities Lending Transactions Accounted for as Secured Borrowings [Line Items]    
Payables under repurchase agreements 9,471 10,579
Payables under securities lending transactions 1,234 717
Obligations to return securities received as collateral 6,260 5,185
Total 16,965 16,481
30 days or less    
Repurchase Agreements, and Securities Lending Transactions Accounted for as Secured Borrowings [Line Items]    
Payables under repurchase agreements 28,467 29,902
Payables under securities lending transactions 18 3
Obligations to return securities received as collateral 173 399
Total 28,658 30,304
31 to 90 days    
Repurchase Agreements, and Securities Lending Transactions Accounted for as Secured Borrowings [Line Items]    
Payables under repurchase agreements 3,349 4,754
Payables under securities lending transactions 0 0
Obligations to return securities received as collateral 862 155
Total 4,211 4,909
Over 90 days    
Repurchase Agreements, and Securities Lending Transactions Accounted for as Secured Borrowings [Line Items]    
Payables under repurchase agreements 1,005 1,146
Payables under securities lending transactions 0 17
Obligations to return securities received as collateral 1,173 308
Total ¥ 2,178 ¥ 1,471