v3.26.1
Stockholders' equity - Summary of Dividends paid (Detail) - JPY (¥)
¥ / shares in Units, ¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Board Resolution Two Thousand Twenty Four May Fourteen [Member]    
Disclosure Of Dividends [Line Items]    
Type of shares   Common stock
Total amount of dividends   ¥ 54,965
Source of dividends   Retained earnings
Dividends per share [1]   ¥ 45
Record date   Mar. 31, 2024
Effective date   Jun. 10, 2024
Board Resolution Two Thousand Twenty Four November Seven [Member]    
Disclosure Of Dividends [Line Items]    
Type of shares   Common stock
Total amount of dividends   ¥ 60,347
Source of dividends   Retained earnings
Dividends per share [2]   ¥ 50
Record date   Sep. 30, 2024
Effective date   Dec. 05, 2024
Board Resolution Two Thousand Twenty Five May Fourteen [Member]    
Disclosure Of Dividends [Line Items]    
Type of shares Common stock  
Total amount of dividends ¥ 60,250  
Source of dividends Retained earnings  
Dividends per share [1] ¥ 10  
Record date Mar. 31, 2025  
Effective date Jun. 02, 2025  
Board Resolution Two Thousand Twenty Five November Eleven [Member]    
Disclosure Of Dividends [Line Items]    
Type of shares Common stock  
Total amount of dividends ¥ 74,714  
Source of dividends Retained earnings  
Dividends per share [2] ¥ 12.5  
Record date Sep. 30, 2025  
Effective date Dec. 05, 2025  
Board Resolution Two Thousand Twenty Six May Eight [Member]    
Disclosure Of Dividends [Line Items]    
Type of shares Common stock  
Total amount of dividends ¥ 73,846  
Source of dividends Retained earnings  
Dividends per share [2] ¥ 12.5  
Record date Mar. 31, 2026  
Effective date Jun. 01, 2026  
[1] The amount prior to the stock split.
[2] The amount after the stock split.