v3.25.2
Goodwill and Other Intangible Assets (Movement in Carrying Amount of Goodwill by Business Segment) (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2023
Apr. 01, 2017
Goodwill [Roll Forward]        
Goodwill, at beginning of period ¥ 1,086,510 ¥ 889,524    
Accumulated impairment losses, at beginning of period (592,752) (592,752)    
Goodwill, net at beginning of period 493,758 296,772    
Goodwill acquired during the fiscal year 213,512 173,267    
Impairment loss (150,089) 0 ¥ (33,553)  
Foreign currency translation adjustments and other 983 23,719    
Goodwill, at end of period 1,301,005 1,086,510 889,524  
Accumulated impairment losses, at end of period (742,841) (592,752) (592,752)  
Goodwill, net at end of period 558,164 493,758 296,772  
Goodwill, fully impaired       ¥ 1,900,019
Operating Segments | Customer business | Retail & Digital Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 15,884 0    
Accumulated impairment losses, at beginning of period 0 0    
Goodwill, net at beginning of period 15,884 0    
Goodwill acquired during the fiscal year 63,730 15,884    
Impairment loss 0      
Foreign currency translation adjustments and other 0 0    
Goodwill, at end of period 79,614 15,884 0  
Accumulated impairment losses, at end of period 0 0 0  
Goodwill, net at end of period 79,614 15,884 0  
Operating Segments | Customer business | Global Corporate & Investment Banking Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 159,231 152,236    
Accumulated impairment losses, at beginning of period (63,568) (63,568)    
Goodwill, net at beginning of period 95,663 88,668    
Goodwill acquired during the fiscal year 0 0    
Impairment loss 0      
Foreign currency translation adjustments and other (253) 6,995    
Goodwill, at end of period 158,978 159,231 152,236  
Accumulated impairment losses, at end of period (63,568) (63,568) (63,568)  
Goodwill, net at end of period 95,410 95,663 88,668  
Operating Segments | Customer business | Global Commercial Banking Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 578,139 481,263    
Accumulated impairment losses, at beginning of period (481,263) (481,263)    
Goodwill, net at beginning of period 96,876 0    
Goodwill acquired during the fiscal year 0 94,320    
Impairment loss (32,388)      
Foreign currency translation adjustments and other (977) 2,556    
Goodwill, at end of period 577,162 578,139 481,263  
Accumulated impairment losses, at end of period (513,651) (481,263) (481,263)  
Goodwill, net at end of period 63,511 96,876 0  
Operating Segments | Customer business | Asset Management & Investor Services Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 330,956 253,725    
Accumulated impairment losses, at beginning of period (47,921) (47,921)    
Goodwill, net at beginning of period 283,035 205,804    
Goodwill acquired during the fiscal year 149,782 63,063    
Impairment loss (117,701)      
Foreign currency translation adjustments and other 2,213 14,168    
Goodwill, at end of period 482,951 330,956 253,725  
Accumulated impairment losses, at end of period (165,622) (47,921) (47,921)  
Goodwill, net at end of period 317,329 283,035 205,804  
Operating Segments | Global Markets Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 2,300 2,300    
Accumulated impairment losses, at beginning of period 0 0    
Goodwill, net at beginning of period 2,300 2,300    
Goodwill acquired during the fiscal year 0 0    
Impairment loss 0      
Foreign currency translation adjustments and other 0 0    
Goodwill, at end of period 2,300 2,300 2,300  
Accumulated impairment losses, at end of period 0 0 0  
Goodwill, net at end of period ¥ 2,300 ¥ 2,300 ¥ 2,300