v3.26.1
Other comprehensive income (loss) - Significant reclassifications out of Accumulated other comprehensive income (loss) (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Affected line items in consolidated statements of income [Line Items]      
Revenue—Other / Non-interest expenses—Other ¥ 241,845 ¥ 223,264 ¥ 175,824
Revenue-Net gain on trading 696,894 580,099 491,611
Income tax expense (165,439) (124,709) (96,630)
Net income (loss) 374,382 347,255 177,220
Net income attributable to noncontrolling interests (12,253) (6,519) (11,357)
Net income (loss) attributable to NHI shareholders 362,129 340,736 165,863
Reclassifications out of accumulated other comprehensive income (loss) [Member] | Cumulative translation adjustments [Member]      
Affected line items in consolidated statements of income [Line Items]      
Revenue—Other / Non-interest expenses—Other 12 (2,027) 358
Income tax expense
Net income (loss) 12 (2,027) 358
Net income attributable to noncontrolling interests
Net income (loss) attributable to NHI shareholders 12 (2,027) 358
Reclassifications out of accumulated other comprehensive income (loss) [Member] | Pension liability adjustment [Member]      
Affected line items in consolidated statements of income [Line Items]      
Non-interest expenses-Compensation and benefits / Revenue-Other (882) (1,464) (1,737)
Income tax expense (39) 374 295
Net income (loss) (921) (1,090) (1,442)
Net income attributable to noncontrolling interests
Net income (loss) attributable to NHI shareholders (921) (1,090) (1,442)
Reclassifications out of accumulated other comprehensive income (loss) [Member] | Own credit adjustments [Member]      
Affected line items in consolidated statements of income [Line Items]      
Revenue-Net gain on trading 1,403 315 597
Income tax expense (410) (103) (126)
Net income (loss) 993 212 471
Net income attributable to noncontrolling interests
Net income (loss) attributable to NHI shareholders ¥ 993 ¥ 212 ¥ 471