v3.26.1
Repurchase Agreements and Securities Lending Transactions Accounted for as Secured Borrowings (Gross Amounts of Liabilities by Remaining Contractual Maturity) (Detail) - JPY (¥)
¥ in Billions
Mar. 31, 2026
Mar. 31, 2025
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Repurchase agreements [1] ¥ 37,732 ¥ 38,395
Securities lending transactions [1] 2,067 1,675
Total 39,799 40,070
Overnight and continuous    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Repurchase agreements 20,073 16,755
Securities lending transactions 1,771 1,303
Total 21,844 18,058
Up to 30 Days    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Repurchase agreements 14,076 17,725
Securities lending transactions 198 302
Total 14,274 18,027
31 to 90 Days    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Repurchase agreements 1,923 1,986
Securities lending transactions 0 0
Total 1,923 1,986
Greater than 90 Days    
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]    
Repurchase agreements 1,659 1,929
Securities lending transactions 99 70
Total ¥ 1,758 ¥ 1,999
[1] The above table does not include securities-for-securities lending transactions of ¥125 billion at March 31, 2025 and ¥—  billion at March 31, 2026, where the MHFG Group acts as lender and receives securities that can be sold or pledged as collateral. In these transactions, the Group recognizes the securities received at fair value within Other assets and the obligation to return those securities as a liability within Other liabilities.