Retained Earnings, Legal Reserve and Dividends (Narrative) (Detail) - JPY (¥)
Mar. 31, 2022
Mar. 31, 2021
Oct. 01, 2005
Apr. 02, 2001
Retained Earnings Appropriated and Transferred [Line Items]        
Legal capital surplus ¥ 5,327,772,000,000 ¥ 5,533,761,000,000    
Common stock and preferred stock issued, Value 2,090,270,000,000 ¥ 2,090,270,000,000    
Code and Japanese GAAP        
Retained Earnings Appropriated and Transferred [Line Items]        
Common stock issued, Value       ¥ 924,400,000,000
Preferred stock issued, Value       222,100,000,000
Legal capital surplus     ¥ 3,577,570,000,000 2,838,693,000,000
Common stock and preferred stock issued, Value     1,383,052,000,000  
Retained earnings     ¥ 757,458,000,000 ¥ 0
Japanese GAAP        
Retained Earnings Appropriated and Transferred [Line Items]        
MUFG's amount available for dividends ¥ 4,440,891,000,000      
Minimum | Banking Law        
Retained Earnings Appropriated and Transferred [Line Items]        
Percentage of aggregate amount of cash dividends and certain appropriations of retained earnings associated with cash set aside as legal reserve 20.00%      
Minimum | Companies Act        
Retained Earnings Appropriated and Transferred [Line Items]        
Percentage of aggregate amount of cash dividends and certain appropriations of retained earnings associated with cash set aside as legal reserve 10.00%      
Maximum | Banking Law        
Retained Earnings Appropriated and Transferred [Line Items]        
Percentage of aggregate amount of legal reserve set aside as an appropriation of retained earnings and the legal capital surplus over stated capital 100.00%      
Percentage of aggregate amount of legal reserve set aside as an appropriation of retained earnings and the legal capital surplus available for dividends over stated capital 100.00%      
Maximum | Companies Act        
Retained Earnings Appropriated and Transferred [Line Items]        
Percentage of aggregate amount of legal reserve set aside as an appropriation of retained earnings and the legal capital surplus over stated capital 25.00%      
Percentage of aggregate amount of legal reserve set aside as an appropriation of retained earnings and the legal capital surplus available for dividends over stated capital 25.00%