v3.26.1
Fair Value Measurements - Additional Information (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Foreign bonds [Member] | Japanese bonds [Member]      
Statements [Line Items]      
Percentage of total investment in bonds 41.00% 32.00%  
Foreign bonds [Member] | US European and other bonds [Member]      
Statements [Line Items]      
Percentage of total investment in bonds 59.00% 68.00%  
Other equity securities [Member]      
Statements [Line Items]      
Non-current assets or disposal groups classified as held for sale ¥ 20,799    
Other equity securities [Member] | Listed stocks on the Japanese stock markets [Member]      
Statements [Line Items]      
Percentage of total investment in stocks 78.00% 79.00%  
Public and corporate bonds [Member]      
Statements [Line Items]      
Non-current assets or disposal groups classified as held for sale ¥ 19,447    
Derivative financial instruments [Member]      
Statements [Line Items]      
Gains Losses On Derivative Transactions 37,445 ¥ (80,831) ¥ (267,190)
Non-current assets held for sale [member]      
Statements [Line Items]      
Assets (liabilities) ¥ 21,322