Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2015
Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	$ 498,759
OTC derivative assets having maturity period of 1 to 5 years	262,124
OTC derivative assets having maturity period of greater than 5 years	162,386
OTC derivative assets cross-maturity netting	(95,513)
Total OTC derivative assets, net of cross-maturity netting	827,756
Cross product counterparty netting	(21,605)
Total OTC derivative assets included in Financial instruments owned	806,151
OTC derivative liabilities having maturity period of 0 to 12 months	466,310
OTC derivative liabilities having maturity period of 1 to 5 years	233,323
OTC derivative liabilities having maturity period of greater than 5 years	170,215
OTC derivative liabilities cross-maturity netting	(95,513)
Total OTC derivative liabilities, net of cross-maturity netting	774,335
Cross product counterparty netting	(21,605)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	752,730
Commodity swaps, options and forwards [Member]
Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	57,079
OTC derivative assets having maturity period of 1 to 5 years	2,674
OTC derivative assets having maturity period of greater than 5 years	23,599
OTC derivative assets cross-maturity netting	(2,915)
Total OTC derivative assets, net of cross-maturity netting	80,437
OTC derivative liabilities having maturity period of 0 to 12 months	68,406
OTC derivative liabilities having maturity period of 1 to 5 years	254
OTC derivative liabilities having maturity period of greater than 5 years	5,377
OTC derivative liabilities cross-maturity netting	(2,915)
Total OTC derivative liabilities, net of cross-maturity netting	71,122
Equity swaps and options [Member]
Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	8,894
OTC derivative assets having maturity period of 1 to 5 years	31,585
OTC derivative assets having maturity period of greater than 5 years	5,657
OTC derivative assets cross-maturity netting	0
Total OTC derivative assets, net of cross-maturity netting	46,136
OTC derivative liabilities having maturity period of 0 to 12 months	4,670
OTC derivative liabilities having maturity period of 1 to 5 years	59,118
OTC derivative liabilities having maturity period of greater than 5 years	19,452
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	83,240
Credit default swaps [Member]
Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities [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	0
OTC derivative assets having maturity period of greater than 5 years	7,442
OTC derivative assets cross-maturity netting	(254)
Total OTC derivative assets, net of cross-maturity netting	7,188
OTC derivative liabilities having maturity period of 0 to 12 months	254
OTC derivative liabilities having maturity period of 1 to 5 years	6,242
OTC derivative liabilities having maturity period of greater than 5 years	2,103
OTC derivative liabilities cross-maturity netting	(254)
Total OTC derivative liabilities, net of cross-maturity netting	8,345
Total return swaps [Member]
Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	10,135
OTC derivative assets having maturity period of 1 to 5 years	377
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(299)
Total OTC derivative assets, net of cross-maturity netting	10,213
OTC derivative liabilities having maturity period of 0 to 12 months	15,733
OTC derivative liabilities having maturity period of 1 to 5 years	1,412
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(299)
Total OTC derivative liabilities, net of cross-maturity netting	16,846
Foreign currency forwards, swaps and options [Member]
Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	376,842
OTC derivative assets having maturity period of 1 to 5 years	48,591
OTC derivative assets having maturity period of greater than 5 years	90
OTC derivative assets cross-maturity netting	(23,179)
Total OTC derivative assets, net of cross-maturity netting	402,344
OTC derivative liabilities having maturity period of 0 to 12 months	326,435
OTC derivative liabilities having maturity period of 1 to 5 years	60,213
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(23,179)
Total OTC derivative liabilities, net of cross-maturity netting	363,469
Fixed income forwards [Member]
Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities [Line Items]
OTC derivative liabilities having maturity period of 0 to 12 months	431
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	431
Interest rate swaps, options and forwards [Member]
Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	45,809
OTC derivative assets having maturity period of 1 to 5 years	178,897
OTC derivative assets having maturity period of greater than 5 years	125,598
OTC derivative assets cross-maturity netting	(68,866)
Total OTC derivative assets, net of cross-maturity netting	281,438
OTC derivative liabilities having maturity period of 0 to 12 months	50,381
OTC derivative liabilities having maturity period of 1 to 5 years	106,084
OTC derivative liabilities having maturity period of greater than 5 years	143,283
OTC derivative liabilities cross-maturity netting	(68,866)
Total OTC derivative liabilities, net of cross-maturity netting	$ 230,882