Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Detail) $ in Thousands	May. 31, 2015 USD ($)
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	$ 264,532
OTC derivative assets having maturity period of 1 to 5 years	205,794
OTC derivative assets having maturity period of greater than 5 years	129,896
OTC derivative assets cross-maturity netting	(84,874)
Total OTC derivative assets, net of cross-maturity netting	515,348
Cross product counterparty netting	(16,998)
Total OTC derivative assets included in Financial instruments owned	498,350
OTC derivative liabilities having maturity period of 0 to 12 months	270,003
OTC derivative liabilities having maturity period of 1 to 5 years	198,085
OTC derivative liabilities having maturity period of greater than 5 years	146,917
OTC derivative liabilities cross-maturity netting	(84,874)
Total OTC derivative liabilities, net of cross-maturity netting	530,131
Cross product counterparty netting	(16,998)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	513,133
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	50,402
OTC derivative assets having maturity period of 1 to 5 years	1,592
OTC derivative assets having maturity period of greater than 5 years	21,717
OTC derivative assets cross-maturity netting	(3,562)
Total OTC derivative assets, net of cross-maturity netting	70,149
OTC derivative liabilities having maturity period of 0 to 12 months	51,982
OTC derivative liabilities having maturity period of 1 to 5 years	693
OTC derivative liabilities having maturity period of greater than 5 years	3,474
OTC derivative liabilities cross-maturity netting	(3,562)
Total OTC derivative liabilities, net of cross-maturity netting	52,587
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	12,791
OTC derivative assets having maturity period of 1 to 5 years	13,371
OTC derivative assets having maturity period of greater than 5 years	5,349
OTC derivative assets cross-maturity netting	0
Total OTC derivative assets, net of cross-maturity netting	31,511
OTC derivative liabilities having maturity period of 0 to 12 months	28,147
OTC derivative liabilities having maturity period of 1 to 5 years	37,353
OTC derivative liabilities having maturity period of greater than 5 years	15,332
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	80,832
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	2,045
OTC derivative assets having maturity period of greater than 5 years	7,067
OTC derivative assets cross-maturity netting	(1,519)
Total OTC derivative assets, net of cross-maturity netting	7,593
OTC derivative liabilities having maturity period of 0 to 12 months	1,064
OTC derivative liabilities having maturity period of 1 to 5 years	1,334
OTC derivative liabilities having maturity period of greater than 5 years	5,636
OTC derivative liabilities cross-maturity netting	(1,519)
Total OTC derivative liabilities, net of cross-maturity netting	6,515
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	10,160
OTC derivative assets having maturity period of 1 to 5 years	2,635
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(2,564)
Total OTC derivative assets, net of cross-maturity netting	10,231
OTC derivative liabilities having maturity period of 0 to 12 months	21,311
OTC derivative liabilities having maturity period of 1 to 5 years	9
OTC derivative liabilities having maturity period of greater than 5 years	1,489
OTC derivative liabilities cross-maturity netting	(2,564)
Total OTC derivative liabilities, net of cross-maturity netting	20,245
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	143,252
OTC derivative assets having maturity period of 1 to 5 years	30,561
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(13,178)
Total OTC derivative assets, net of cross-maturity netting	160,635
OTC derivative liabilities having maturity period of 0 to 12 months	121,295
OTC derivative liabilities having maturity period of 1 to 5 years	62,607
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(13,178)
Total OTC derivative liabilities, net of cross-maturity netting	170,724
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	278
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	278
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	47,927
OTC derivative assets having maturity period of 1 to 5 years	155,590
OTC derivative assets having maturity period of greater than 5 years	95,763
OTC derivative assets cross-maturity netting	(64,051)
Total OTC derivative assets, net of cross-maturity netting	235,229
OTC derivative liabilities having maturity period of 0 to 12 months	45,926
OTC derivative liabilities having maturity period of 1 to 5 years	96,089
OTC derivative liabilities having maturity period of greater than 5 years	120,986
OTC derivative liabilities cross-maturity netting	(64,051)
Total OTC derivative liabilities, net of cross-maturity netting	$ 198,950