v3.26.1
Financing receivables - Analysis of each class of loans not carried at fair value using internal ratings or equivalent credit quality indicators (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
 [1],[3]
Mar. 31, 2025
 [4],[5]
Financing receivable, recorded investment [Line items]    
Current year [2] ¥ 2,665,189 ¥ 439,155
Year before current year [2] 275,725 1,053,438
Two years before current year [2] 175,467 336,293
Three years before current year [2] 165,740 137,443
Four years before current year [2] 234,348 109,072
More than five year before current year [2] 347,907 867,118
Revolving [2] 1,101,142 908,121
Total loans [2] 4,965,518 3,850,640
AAA-BBB [Member] | Secured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 461,911 119,134
Year before current year [2] 2,166 231,869
Two years before current year [2] 1,248 2,837
Three years before current year [2] 199 7,517
Four years before current year [2] 10,700 5,000
More than five year before current year [2] 13,309 23,453
Revolving [2]
Total loans [2] 489,533 389,810
AAA-BBB [Member] | Unsecured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 10,564 4,500
Year before current year [2] 1,500 1,377
Two years before current year [2] 300 300
Three years before current year [2] 835 1,735
Four years before current year [2] 3,988 7,700
More than five year before current year [2] 24,529 23,875
Revolving [2]
Total loans [2] 41,716 39,487
AAA-BBB [Member] | Short-term secured margin loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
AAA-BBB [Member] | Secured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 728,870 58,325
Year before current year [2] 228,451 289,986
Two years before current year [2] 114,889 266,380
Three years before current year [2] 103,943 89,955
Four years before current year [2] 215,395 90,419
More than five year before current year [2] 146,352 159,346
Revolving [2] 433,637 385,419
Total loans [2] 1,971,537 1,339,830
AAA-BBB [Member] | Unsecured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
AAA-BBB [Member] | Advances to affiliated companies [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 1,000
Year before current year [2]
Two years before current year [2] 8
Three years before current year [2] 3,000 3,000
Four years before current year [2] 1,000
More than five year before current year [2]
Revolving [2]
Total loans [2] 4,000 4,008
BB-CCC [Member] | Secured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 314,914 125,213
Year before current year [2] 1,006 219,055
Two years before current year [2] 15,000
Three years before current year [2] 21,086 8,439
Four years before current year [2]
More than five year before current year [2] 778 1,151
Revolving [2]
Total loans [2] 337,784 368,858
BB-CCC [Member] | Unsecured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 101 703
Year before current year [2] 803 1,000
Two years before current year [2] 1,656 756
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2] 1,500 2,139
Revolving [2]
Total loans [2] 4,060 4,598
BB-CCC [Member] | Short-term secured margin loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
BB-CCC [Member] | Secured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 47,531 1
Year before current year [2] 41,777 32,529
Two years before current year [2] 57,374 50,893
Three years before current year [2] 34,605 25,157
Four years before current year [2] 3,698 4,424
More than five year before current year [2] 9,646 41,270
Revolving [2] 280,651 199,701
Total loans [2] 475,282 353,975
BB-CCC [Member] | Unsecured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
BB-CCC [Member] | Advances to affiliated companies [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
CC-D [Member] | Secured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
CC-D [Member] | Unsecured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
CC-D [Member] | Short-term secured margin loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
CC-D [Member] | Secured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2] 1,944
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2] 1,944
CC-D [Member] | Unsecured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
CC-D [Member] | Advances to affiliated companies [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
Others [Member] | Secured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2],[6] 304,342
Year before current year [2],[6] 243,034
Two years before current year [2],[6]
Three years before current year [2],[6]
Four years before current year [2],[6]
More than five year before current year [2],[6]
Revolving [2],[6]
Total loans [2],[6] 304,342 243,034
Others [Member] | Unsecured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
Others [Member] | Short-term secured margin loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2],[6] 747,640
Year before current year [2],[6]
Two years before current year [2],[6]
Three years before current year [2],[6]
Four years before current year [2],[6]
More than five year before current year [2],[6] 474,019
Revolving [2],[6] 386,753 322,917
Total loans [2],[6] 1,134,393 796,936
Others [Member] | Secured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2],[6] 48,128 131,132
Year before current year [2],[6] 34,567
Two years before current year [2],[6]
Three years before current year [2],[6] 1,640
Four years before current year [2],[6]
More than five year before current year [2],[6] 115
Revolving [2],[6] 101 84
Total loans [2],[6] 48,229 167,538
Others [Member] | Unsecured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 188 147
Year before current year [2] 22 21
Two years before current year [2] 119
Three years before current year [2] 128
Four years before current year [2] 567 529
More than five year before current year [2] 151,793 141,750
Revolving [2]
Total loans [2] 152,698 142,566
Others [Member] | Advances to affiliated companies [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2]
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2]
Revolving [2]
Total loans [2]
Total [Member] | Secured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 1,081,167 244,347
Year before current year [2] 3,172 693,958
Two years before current year [2] 1,248 17,837
Three years before current year [2] 21,285 15,956
Four years before current year [2] 10,700 5,000
More than five year before current year [2] 14,087 24,604
Revolving [2]
Total loans [2] 1,131,659 1,001,702
Total [Member] | Unsecured loans at banks [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 10,665 5,203
Year before current year [2] 2,303 2,377
Two years before current year [2] 1,956 1,056
Three years before current year [2] 835 1,735
Four years before current year [2] 3,988 7,700
More than five year before current year [2] 26,029 26,014
Revolving [2]
Total loans [2] 45,776 44,085
Total [Member] | Short-term secured margin loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 747,640
Year before current year [2]
Two years before current year [2]
Three years before current year [2]
Four years before current year [2]
More than five year before current year [2] 474,019
Revolving [2] 386,753 322,917
Total loans [2] 1,134,393 796,936
Total [Member] | Secured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 824,529 189,458
Year before current year [2] 270,228 357,082
Two years before current year [2] 172,263 317,273
Three years before current year [2] 140,492 116,752
Four years before current year [2] 219,093 94,843
More than five year before current year [2] 155,998 200,731
Revolving [2] 714,389 585,204
Total loans [2] 2,496,992 1,861,343
Total [Member] | Unsecured corporate loans [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 188 147
Year before current year [2] 22 21
Two years before current year [2] 119
Three years before current year [2] 128
Four years before current year [2] 567 529
More than five year before current year [2] 151,793 141,750
Revolving [2]
Total loans [2] 152,698 142,566
Total [Member] | Advances to affiliated companies [Member]    
Financing receivable, recorded investment [Line items]    
Current year [2] 1,000
Year before current year [2]
Two years before current year [2] 8
Three years before current year [2] 3,000 3,000
Four years before current year [2] 1,000
More than five year before current year [2]
Revolving [2]
Total loans [2] ¥ 4,000 ¥ 4,008
[1] Amounts are presented by fiscal year of origination.
[2] The amounts are aggregated by reference to the year in which the contract became effective, rather than the date of loan drawdown.
[3] The amounts of write offs for the year ended March 31, 2026 were not significant.
[4] Amounts are presented by calendar year of origination.
[5] The amounts of write offs for the year ended March 31, 2025 were not significant.
[6] Relates to collateralized exposures where a specified ratio of LTV is maintained.