v3.26.1
Goodwill and intangible assets - Summary of Changes In Goodwill (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Disclosure of reconciliation of changes in goodwill [line items]    
Balance at beginning of the fiscal year ¥ 1,508,721 ¥ 1,487,100
Increase (decrease) due to:    
Acquisitions 88,058 44,424
Disposals or classified as held for sale (1,245) 0
Classified as held for distribution to owners (10,834)
Impairment losses (17,430)  
Translation adjustments 106,636 (22,803)
Total changes 165,185 21,621
Balance at end of the fiscal year 1,673,906 1,508,721
Gross carrying amount [member]    
Disclosure of reconciliation of changes in goodwill [line items]    
Balance at beginning of the fiscal year 1,903,617 1,884,627
Increase (decrease) due to:    
Balance at end of the fiscal year 2,084,956 1,903,617
Accumulated impairment [member]    
Disclosure of reconciliation of changes in goodwill [line items]    
Balance at beginning of the fiscal year (394,896) (397,527)
Increase (decrease) due to:    
Balance at end of the fiscal year ¥ (411,050) ¥ (394,896)