v3.25.2
Severance Indemnities and Pension Plans (Amounts Recognized in Accumulated OCI) (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2025
Mar. 31, 2024
Domestic, Japan | Pension benefits and SIPs    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial loss (gain) ¥ (638,775) ¥ (538,886)
Prior service cost 807 525
Gross amount recognized in Accumulated OCI (637,968) (538,361)
Taxes 152,200 121,569
Net amount recognized in Accumulated OCI (485,768) (416,792)
Foreign offices and subsidiaries | Pension benefits    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial loss (gain) 34,990 38,066
Prior service cost (2,467) (1,743)
Gross amount recognized in Accumulated OCI 32,523 36,323
Taxes (9,134) (10,923)
Net amount recognized in Accumulated OCI 23,389 25,400
Foreign offices and subsidiaries | Other benefits    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial loss (gain) 1,685 2,105
Prior service cost (659) (1,114)
Gross amount recognized in Accumulated OCI 1,026 991
Taxes (281) (306)
Net amount recognized in Accumulated OCI ¥ 745 ¥ 685