v3.26.1
Employee benefit plans - Information about fair value of plan assets (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets ¥ 202,368 ¥ 208,523 ¥ 219,869
Level 1 [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 19,954 24,713  
Level 1 [Member] | Private equity and pooled investments [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets [1]  
Level 1 [Member] | Japanese government securities [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 19,954 24,713  
Level 1 [Member] | Investment trust funds and other [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets [2],[3]  
Level 1 [Member] | Life insurance company general accounts [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets  
Level 1 [Member] | Other assets [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets  
Level 2 [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 114,444 118,567  
Level 2 [Member] | Private equity and pooled investments [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets [1] 584 1,545  
Level 2 [Member] | Japanese government securities [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets  
Level 2 [Member] | Investment trust funds and other [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets [2],[3] 10,026 10,535  
Level 2 [Member] | Life insurance company general accounts [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 74,968 75,067  
Level 2 [Member] | Other assets [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 28,866 31,420  
Level 3 [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 29,878 29,714 43,343
Level 3 [Member] | Private equity and pooled investments [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 9,139 [1] 9,418 [1] 16,321
Level 3 [Member] | Japanese government securities [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets  
Level 3 [Member] | Investment trust funds and other [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 20,739 [2],[3] 20,296 [2],[3] ¥ 27,022
Level 3 [Member] | Life insurance company general accounts [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets  
Level 3 [Member] | Other assets [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets  
Fair value [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 164,276 172,994  
Fair value [Member] | Private equity and pooled investments [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets [1] 9,723 10,963  
Fair value [Member] | Japanese government securities [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 19,954 24,713  
Fair value [Member] | Investment trust funds and other [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets [2],[3] 30,765 30,831  
Fair value [Member] | Life insurance company general accounts [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets 74,968 75,067  
Fair value [Member] | Other assets [Member]      
Pension plans, postretirement and other employee benefits [Line items]      
Fair value of plan assets ¥ 28,866 ¥ 31,420  
[1] Includes corporate type equity investments.
[2] Certain plan assets that are carried at fair value using net asset value per share as a practical expedient have not been classified in the fair value hierarchy. As of March 31, 2025 and 2026, the fair value of these assets was ¥35,529 million and ¥38,092 million, respectively.
[3] Includes primarily debt investment funds. Hedge funds and real estate funds are also included.