v3.26.1
Retirement Benefits - Plan Assets (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Disclosure of fair value of plan assets [Line Items]      
Total ¥ (659,730) ¥ (443,867) ¥ (330,739)
Plan assets [member]      
Disclosure of fair value of plan assets [Line Items]      
Total 2,034,686 1,804,994 ¥ 1,820,599
Plan assets [member] | Level 1 [member]      
Disclosure of fair value of plan assets [Line Items]      
Total 888,337 788,779  
Plan assets [member] | Level 2 and 3 of fair value hierarchy [member]      
Disclosure of fair value of plan assets [Line Items]      
Total 1,146,349 1,016,215  
Plan assets [member] | Pension funds [member]      
Disclosure of fair value of plan assets [Line Items]      
Equity instruments 244,015 278,692  
Debt instruments 215,644 213,307  
General account of life insurance companies 22,715 22,355  
Other investments and short-term assets 860,965 705,777  
Plan assets [member] | Pension funds [member] | Level 1 [member]      
Disclosure of fair value of plan assets [Line Items]      
Equity instruments 155,581 160,285  
Debt instruments 5,377 8,955  
General account of life insurance companies 138 160  
Other investments and short-term assets 49,947 48,128  
Plan assets [member] | Pension funds [member] | Level 2 and 3 of fair value hierarchy [member]      
Disclosure of fair value of plan assets [Line Items]      
Equity instruments 88,434 118,407  
Debt instruments 210,267 204,352  
General account of life insurance companies 22,577 22,195  
Other investments and short-term assets 811,018 657,649  
Plan assets [member] | Retirement benefit trusts [member]      
Disclosure of fair value of plan assets [Line Items]      
Equity instruments 545,890 549,586  
Other short-term assets 145,457 35,277  
Plan assets [member] | Retirement benefit trusts [member] | Level 1 [member]      
Disclosure of fair value of plan assets [Line Items]      
Equity instruments 541,865 546,424  
Other short-term assets 135,429 24,827  
Plan assets [member] | Retirement benefit trusts [member] | Level 2 and 3 of fair value hierarchy [member]      
Disclosure of fair value of plan assets [Line Items]      
Equity instruments 4,025 3,162  
Other short-term assets ¥ 10,028 ¥ 10,450