v3.26.1
Goodwill and Other Intangible Assets (Movement in Carrying Amount of Goodwill by Business Segment) (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Apr. 01, 2017
Goodwill [Roll Forward]        
Goodwill, at beginning of period ¥ 1,301,005 ¥ 1,086,510    
Accumulated impairment losses, at beginning of period (742,841) (592,752)    
Goodwill, net at beginning of period 558,164 493,758    
Goodwill acquired during the fiscal year 82,953 213,512    
Impairment loss (97,475) (150,089) ¥ 0  
Foreign currency translation adjustments and other 22,894 983    
Goodwill, at end of period 1,406,852 1,301,005 1,086,510  
Accumulated impairment losses, at end of period (840,316) (742,841) (592,752)  
Goodwill, net at end of period 566,536 558,164 493,758  
Goodwill, fully impaired       ¥ 1,900,019
Operating Segments | Customer business | Retail & Digital Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 79,614 15,884    
Accumulated impairment losses, at beginning of period 0 0    
Goodwill, net at beginning of period 79,614 15,884    
Goodwill acquired during the fiscal year 20,117 63,730    
Impairment loss (5,149) 0    
Foreign currency translation adjustments and other 0 0    
Goodwill, at end of period 99,731 79,614 15,884  
Accumulated impairment losses, at end of period (5,149) 0 0  
Goodwill, net at end of period 94,582 79,614 15,884  
Operating Segments | Customer business | Global Corporate & Investment Banking Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 158,978 159,231    
Accumulated impairment losses, at beginning of period (63,568) (63,568)    
Goodwill, net at beginning of period 95,410 95,663    
Goodwill acquired during the fiscal year 0 0    
Impairment loss 0 0    
Foreign currency translation adjustments and other 3,915 (253)    
Goodwill, at end of period 162,893 158,978 159,231  
Accumulated impairment losses, at end of period (63,568) (63,568) (63,568)  
Goodwill, net at end of period 99,325 95,410 95,663  
Operating Segments | Customer business | Global Commercial Banking Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 577,162 578,139    
Accumulated impairment losses, at beginning of period (513,651) (481,263)    
Goodwill, net at beginning of period 63,511 96,876    
Goodwill acquired during the fiscal year 62,836 0    
Impairment loss 0 (32,388)    
Foreign currency translation adjustments and other 5,664 (977)    
Goodwill, at end of period 645,662 577,162 578,139  
Accumulated impairment losses, at end of period (513,651) (513,651) (481,263)  
Goodwill, net at end of period 132,011 63,511 96,876  
Operating Segments | Customer business | Asset Management & Investor Services Business Group        
Goodwill [Roll Forward]        
Goodwill, at beginning of period 482,951 330,956    
Accumulated impairment losses, at beginning of period (165,622) (47,921)    
Goodwill, net at beginning of period 317,329 283,035    
Goodwill acquired during the fiscal year 0 149,782    
Impairment loss (92,326) (117,701)    
Foreign currency translation adjustments and other 13,315 2,213    
Goodwill, at end of period 496,266 482,951 330,956  
Accumulated impairment losses, at end of period (257,948) (165,622) (47,921)  
Goodwill, net at end of period 238,318 317,329 283,035  
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 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