Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Detail) $ in Thousands	Feb. 28, 2017 USD ($)
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	$ 94,634
OTC derivative assets having maturity period of 1 to 5 years	209,275
OTC derivative assets having maturity period of greater than 5 years	124,873
OTC derivative assets cross-maturity netting	(79,776)
Total OTC derivative assets, net of cross-maturity netting	349,006
Cross product counterparty netting	(1,512)
Total OTC derivative assets included in Financial instruments owned	347,494
OTC derivative liabilities having maturity period of 0 to 12 months	93,051
OTC derivative liabilities having maturity period of 1 to 5 years	152,292
OTC derivative liabilities having maturity period of greater than 5 years	98,866
OTC derivative liabilities cross-maturity netting	(79,776)
Total OTC derivative liabilities, net of cross-maturity netting	264,433
Cross product counterparty netting	(1,512)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	262,921
Equity Swaps And Options [Member]
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	18,536
OTC derivative assets having maturity period of 1 to 5 years	3,271
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	21,807
OTC derivative liabilities having maturity period of 0 to 12 months	13,148
OTC derivative liabilities having maturity period of 1 to 5 years	17,187
OTC derivative liabilities having maturity period of greater than 5 years	1,908
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	32,243
Credit Default Swap [Member]
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	14,487
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	14,487
OTC derivative liabilities having maturity period of 0 to 12 months	178
OTC derivative liabilities having maturity period of 1 to 5 years	13,155
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	13,333
Total Return Swap [Member]
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	6,384
OTC derivative assets having maturity period of 1 to 5 years	771
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(38)
Total OTC derivative assets, net of cross-maturity netting	7,117
OTC derivative liabilities having maturity period of 0 to 12 months	20,221
OTC derivative liabilities having maturity period of 1 to 5 years	2,391
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(38)
Total OTC derivative liabilities, net of cross-maturity netting	22,574
Foreign Currency Forwards Swaps And Options [Member]
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	37,502
OTC derivative assets having maturity period of 1 to 5 years	37,500
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(13,111)
Total OTC derivative assets, net of cross-maturity netting	61,891
OTC derivative liabilities having maturity period of 0 to 12 months	39,883
OTC derivative liabilities having maturity period of 1 to 5 years	27,382
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(13,111)
Total OTC derivative liabilities, net of cross-maturity netting	54,154
Fixed Income Forwards [Member]
Derivative [Line Items]
OTC derivative liabilities having maturity period of 0 to 12 months	275
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	275
Interest Rate Swaps, Options and Forwards [Member]
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	32,212
OTC derivative assets having maturity period of 1 to 5 years	153,246
OTC derivative assets having maturity period of greater than 5 years	124,873
OTC derivative assets cross-maturity netting	(66,627)
Total OTC derivative assets, net of cross-maturity netting	243,704
OTC derivative liabilities having maturity period of 0 to 12 months	19,346
OTC derivative liabilities having maturity period of 1 to 5 years	92,177
OTC derivative liabilities having maturity period of greater than 5 years	96,958
OTC derivative liabilities cross-maturity netting	(66,627)
Total OTC derivative liabilities, net of cross-maturity netting	$ 141,854