v3.25.2
Income taxes - Additional Information (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2027
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2023
Statements [Line Items]        
Temporary differences associated with investments in subsidiaries, branches and associates and interests in joint arrangements for which deferred tax liabilities have not been recognised   ¥ 1,117,684 ¥ 1,122,164  
Statutory tax rate   31.50% 31.50% 31.50%
Undistributed earnings   ¥ 6,678,168 ¥ 6,002,407  
Deferred tax expense (income) recognised in profit or loss   61,544    
Remeasurement gain for the pre-owned equity interest   116,939    
Deferred tax assets   559,284 499,550  
Deferred tax liabilities   175,228 166,424  
Tax expense (income)   313,839 288,168 ¥ 262,723
Increase decrease in tax expenses from repayment of capital from a subsidiary   48,373    
Increase decrease in tax expenses from dissolution of a subsidiary   35,278    
Country of domicile [member]        
Statements [Line Items]        
Tax expense (income)   120,578 169,821 157,745
Foreign countries [member]        
Statements [Line Items]        
Tax expense (income)   ¥ 193,261 118,347 ¥ 104,978
Unused tax credits [member]        
Statements [Line Items]        
Description of expiry date of deductible temporary differences, unused tax losses and unused tax credits   As of March 31, 2024 and 2025, the expected expiration period of the tax credit carryforwards for which no deferred tax asset is recognized was mostly within 5 years.    
Undistributed Earnings Of Foreign Subsidiaries And Corporate Joint Ventures [Member]        
Statements [Line Items]        
Undistributed earnings   ¥ 17,883 17,955  
Unrealised foreign exchange gains (losses) [member]        
Statements [Line Items]        
Deferred tax assets   173,711 275,810  
Deferred tax liabilities   ¥ 1,047,225 ¥ 1,228,503  
Change of applicable tax rate [member]        
Statements [Line Items]        
Statutory tax rate 32.30%