v3.26.1
Retirement Benefits - Additional Information (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Disclosure of defined benefit plans [Line Items]      
Expected contributions to defined benefit plans for the fiscal year ending March 31, 2027 ¥ 12,161    
Contributions charged to expense for the Employees' Pension Insurance Plan 17,020 ¥ 16,204 ¥ 14,579
Selling, general and administrative expense [member]      
Disclosure of defined benefit plans [Line Items]      
Contributions charged to expense for the Employees' Pension Insurance Plan ¥ 45,478 ¥ 43,968 ¥ 40,974
Average life expectancy at age 60 [member]      
Disclosure of defined benefit plans [Line Items]      
Current average remaining life expectancy of individual male employees retiring at age 60 24 years 24 years 24 years
Current average remaining life expectancy of individual female employees retiring at age 60 29 years 29 years 29 years
Retirement benefit trusts [member] | Equity investments where voting rights were retained [member]      
Disclosure of defined benefit plans [Line Items]      
Fair values of equity instruments where company retained voting rights ¥ 534,202 ¥ 539,742  
Fair values of equity instruments where company retained voting rights, percentage of fair values of plan assets 26.30% 29.90%