v3.26.1
Income taxes - Reconciliation of the effective income tax rate (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Income Tax Expense (Benefit), Amount:      
Japan national tax rate ¥ 138,194    
Japan local tax, net of national tax effect [1] 29,213    
Total ¥ 165,439 ¥ 124,709 ¥ 96,630
Income Tax Rate, Percent:      
Effective statutory tax rate   31.00% 31.00%
Japan national tax rate, rate 25.60%    
Japan local tax, net of national tax effect, rate [1] 5.40%    
Changes in deferred tax valuation allowances, rate   (5.30%) 3.90%
Additional taxable income, rate   1.30% 0.20%
Non-deductible expenses, rate   3.20% 6.00%
Non-taxable income, rate   (1.60%) (2.50%)
Dividends from foreign subsidiaries, rate   0.00% 0.00%
Tax effect of undistributed earnings of foreign subsidiaries, rate   0.00% (0.20%)
Different tax rate applicable to income (loss) of foreign subsidiaries, rate   (2.50%) (0.20%)
Effect of changes in foreign tax laws, rate   0.00% 0.00%
Effect of changes in domestic tax laws, rate   0.40%  
Tax benefit recognized on the outside basis differences for investment in subsidiaries and affiliates, rate   0.00% 0.00%
Other (Percent)   (0.10%) (2.90%)
Effective tax rate 30.60% 26.40% 35.30%
Domestic tax effects [Member]      
Income Tax Expense (Benefit), Amount:      
Changes in deferred tax valuation allowances ¥ 4,319    
Stock-based compensation awards, amount 10,610    
Non-taxable income amount (2,699)    
Tax credits, amount (2,699)    
Unrecognized tax benefit 5,039    
Effect of cross-border tax laws, amount 3,239    
Other (Amount) (4,310)    
Other. amount ¥ 3,426    
Income Tax Rate, Percent:      
Changes in deferred tax valuation allowances, rate 0.80%    
Non-taxable income, rate (0.50%)    
Tax credits, rate (0.50%)    
Effect of cross-border tax laws, Percent 0.60%    
Unrecognized tax benefit 0.90%    
Other (Percent) (0.80%)    
Stock-based compensation awards, Percent 2.00%    
Other, Percent 0.60%    
US | Foreign tax effects [Member]      
Income Tax Expense (Benefit), Amount:      
Changes in deferred tax valuation allowances [2] ¥ (43,725)    
Other (Amount) ¥ 2,159    
Income Tax Rate, Percent:      
Changes in deferred tax valuation allowances, rate [2] (8.10%)    
Other (Percent) 0.40%    
UK | Foreign tax effects [Member]      
Income Tax Expense (Benefit), Amount:      
Changes in deferred tax valuation allowances ¥ 9,717    
Other (Amount) ¥ (1,619)    
Income Tax Rate, Percent:      
Changes in deferred tax valuation allowances, rate 1.80%    
Other (Percent) (0.30%)    
INDIA | Foreign tax effects [Member]      
Income Tax Expense (Benefit), Amount:      
Different tax rate applicable to income (loss) of foreign subsidiaries ¥ 7,557    
Other (Amount) ¥ 540    
Income Tax Rate, Percent:      
Different tax rate applicable to income (loss) of foreign subsidiaries, rate 1.40%    
Other (Percent) 0.10%    
Other Foreign [Member] | Foreign tax effects [Member]      
Income Tax Expense (Benefit), Amount:      
Other jurisdictions ¥ 6,478    
Income Tax Rate, Percent:      
Other jurisdictions, rate 1.20%    
[1] The tax effects in this category primarily relate to local Japanese taxes arising in Tokyo
[2] Primarily due to improved profitability and increase in taxable temporary differences resulted in release of certain valuation allowance.