v3.26.1
Severance Indemnities and Pension Plans (Amounts Recognized in Accumulated OCI) (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Domestic, Japan | Pension benefits and SIPs    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial loss (gain) ¥ (947,771) ¥ (638,775)
Prior service cost 416 807
Gross amount recognized in Accumulated OCI (947,355) (637,968)
Taxes 249,543 152,200
Net amount recognized in Accumulated OCI (697,812) (485,768)
Foreign offices and subsidiaries | Pension benefits    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial loss (gain) 31,862 34,990
Prior service cost (1,903) (2,467)
Gross amount recognized in Accumulated OCI 29,959 32,523
Taxes (7,889) (9,134)
Net amount recognized in Accumulated OCI 22,070 23,389
Foreign offices and subsidiaries | Other benefits    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial loss (gain) 704 1,685
Prior service cost (234) (659)
Gross amount recognized in Accumulated OCI 470 1,026
Taxes (120) (281)
Net amount recognized in Accumulated OCI ¥ 350 ¥ 745