v3.26.1
Loans - Credit Quality Information of Loans Based on MHFG Group's Internal Rating System (Parenthetical) (Detail) - JPY (¥)
¥ in Billions
Mar. 31, 2026
Mar. 31, 2025
Financing Receivables Impaired    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Direct Financing Lease, Lease Receivable ¥ 169 ¥ 166