v3.26.1
Employee benefit plans - Information about plan assets for which Level 3 inputs are utilized to determine fair value (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Pension plans, postretirement and other employee benefits [Line items]    
Fair value of plan assets at beginning of year ¥ 208,523 ¥ 219,869
Fair value of plan assets at end of year 202,368 208,523
Level 3 [Member]    
Pension plans, postretirement and other employee benefits [Line items]    
Fair value of plan assets at beginning of year 29,714 43,343
Unrealized and realized gains / loss 1,630 (4,853)
Purchases / sales and other settlement (1,466) (8,776)
Fair value of plan assets at end of year 29,878 29,714
Level 3 [Member] | Private equity and pooled investments [Member]    
Pension plans, postretirement and other employee benefits [Line items]    
Fair value of plan assets at beginning of year 9,418 [1] 16,321
Unrealized and realized gains / loss 415 (3,608)
Purchases / sales and other settlement (694) (3,295)
Fair value of plan assets at end of year [1] 9,139 9,418
Level 3 [Member] | Investment trust funds and other [Member]    
Pension plans, postretirement and other employee benefits [Line items]    
Fair value of plan assets at beginning of year 20,296 [2],[3] 27,022
Unrealized and realized gains / loss 1,215 (1,245)
Purchases / sales and other settlement (772) (5,481)
Fair value of plan assets at end of year [2],[3] ¥ 20,739 ¥ 20,296
[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.