v3.25.2
Severance Indemnities and Pension Plans (Assumed Health Care Cost Trend Rates and Effect of a One-percentage-point Change for Foreign Offices and Subsidiaries) (Detail)
Mar. 31, 2025
Mar. 31, 2024
Retirement Benefits [Abstract]    
Initial trend rate 8.00% 7.50%
Ultimate trend rate 4.00% 4.00%