Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Detail) $ in Thousands	Feb. 28, 2018 USD ($)
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	$ 117,562
OTC derivative assets having maturity period of 1 to 5 years	124,647
OTC derivative assets having maturity period of greater than 5 years	84,770
OTC derivative assets cross-maturity netting	(88,014)
Total OTC derivative assets, net of cross-maturity netting	238,965
Cross product counterparty netting	(20,558)
Total OTC derivative assets included in Financial instruments owned	218,407
OTC derivative liabilities having maturity period of 0 to 12 months	153,673
OTC derivative liabilities having maturity period of 1 to 5 years	422,922
OTC derivative liabilities having maturity period of greater than 5 years	231,968
OTC derivative liabilities cross-maturity netting	(88,014)
Total OTC derivative liabilities, net of cross-maturity netting	720,549
Cross product counterparty netting	(20,558)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	699,991
Exchange traded derivative assets	58,700
Cash collateral received	127,600
Exchange traded derivative liabilities, with fair value	518,400
Cash collateral pledged	368,700
Equity swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	1,156
OTC derivative assets having maturity period of 1 to 5 years	6,907
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	0
Total OTC derivative assets, net of cross-maturity netting	8,063
OTC derivative liabilities having maturity period of 0 to 12 months	15,297
OTC derivative liabilities having maturity period of 1 to 5 years	170,529
OTC derivative liabilities having maturity period of greater than 5 years	4,057
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	189,883
Credit default swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	0
OTC derivative assets having maturity period of 1 to 5 years	12,996
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	0
Total OTC derivative assets, net of cross-maturity netting	12,996
OTC derivative liabilities having maturity period of 0 to 12 months	31
OTC derivative liabilities having maturity period of 1 to 5 years	8,994
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	9,025
Total return swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	28,882
OTC derivative assets having maturity period of 1 to 5 years	5,843
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(1,595)
Total OTC derivative assets, net of cross-maturity netting	33,130
OTC derivative liabilities having maturity period of 0 to 12 months	46,255
OTC derivative liabilities having maturity period of 1 to 5 years	115,708
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(1,595)
Total OTC derivative liabilities, net of cross-maturity netting	160,368
Foreign currency forwards, swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	56,436
OTC derivative assets having maturity period of 1 to 5 years	561
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(257)
Total OTC derivative assets, net of cross-maturity netting	56,740
OTC derivative liabilities having maturity period of 0 to 12 months	49,425
OTC derivative liabilities having maturity period of 1 to 5 years	374
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(257)
Total OTC derivative liabilities, net of cross-maturity netting	49,542
Fixed income forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	39
OTC derivative assets having maturity period of 1 to 5 years	0
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	0
Total OTC derivative assets, net of cross-maturity netting	39
OTC derivative liabilities having maturity period of 0 to 12 months	4,669
OTC derivative liabilities having maturity period of 1 to 5 years	0
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	4,669
Interest rate swaps, options and forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	31,049
OTC derivative assets having maturity period of 1 to 5 years	98,340
OTC derivative assets having maturity period of greater than 5 years	84,770
OTC derivative assets cross-maturity netting	(86,162)
Total OTC derivative assets, net of cross-maturity netting	127,997
OTC derivative liabilities having maturity period of 0 to 12 months	37,996
OTC derivative liabilities having maturity period of 1 to 5 years	127,317
OTC derivative liabilities having maturity period of greater than 5 years	227,911
OTC derivative liabilities cross-maturity netting	(86,162)
Total OTC derivative liabilities, net of cross-maturity netting	$ 307,062