Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Detail) $ in Thousands	Aug. 31, 2018 USD ($)
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	$ 113,887
OTC derivative assets having maturity period of 1 to 5 years	174,588
OTC derivative assets having maturity period of greater than 5 years	98,168
OTC derivative assets cross-maturity netting	(105,568)
Total OTC derivative assets, net of cross-maturity netting	281,075
Cross product counterparty netting	(32,615)
Total OTC derivative assets included in Financial instruments owned	248,460
OTC derivative liabilities having maturity period of 0 to 12 months	135,917
OTC derivative liabilities having maturity period of 1 to 5 years	288,852
OTC derivative liabilities having maturity period of greater than 5 years	211,617
OTC derivative liabilities cross-maturity netting	(105,568)
Total OTC derivative liabilities, net of cross-maturity netting	530,818
Cross product counterparty netting	(32,615)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	498,203
Exchange traded derivative assets	85,200
Cash collateral received	158,200
Exchange traded derivative liabilities, with fair value	472,000
Cash collateral pledged	278,600
Equity swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	10,226
OTC derivative assets having maturity period of 1 to 5 years	8,071
OTC derivative assets having maturity period of greater than 5 years	2,195
OTC derivative assets cross-maturity netting	0
Total OTC derivative assets, net of cross-maturity netting	20,492
OTC derivative liabilities having maturity period of 0 to 12 months	15,125
OTC derivative liabilities having maturity period of 1 to 5 years	92,491
OTC derivative liabilities having maturity period of greater than 5 years	13,048
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	120,664
Credit default swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	82
OTC derivative assets having maturity period of 1 to 5 years	17,846
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(11)
Total OTC derivative assets, net of cross-maturity netting	17,917
OTC derivative liabilities having maturity period of 0 to 12 months	17
OTC derivative liabilities having maturity period of 1 to 5 years	10,374
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(11)
Total OTC derivative liabilities, net of cross-maturity netting	10,380
Total return swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	46,036
OTC derivative assets having maturity period of 1 to 5 years	29,910
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(4,334)
Total OTC derivative assets, net of cross-maturity netting	71,612
OTC derivative liabilities having maturity period of 0 to 12 months	67,526
OTC derivative liabilities having maturity period of 1 to 5 years	19,806
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(4,334)
Total OTC derivative liabilities, net of cross-maturity netting	82,998
Foreign currency forwards, swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	42,326
OTC derivative assets having maturity period of 1 to 5 years	22,130
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(9,550)
Total OTC derivative assets, net of cross-maturity netting	54,906
OTC derivative liabilities having maturity period of 0 to 12 months	36,176
OTC derivative liabilities having maturity period of 1 to 5 years	17,496
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(9,550)
Total OTC derivative liabilities, net of cross-maturity netting	44,122
Fixed income forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	2,113
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	2,113
OTC derivative liabilities having maturity period of 0 to 12 months	685
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	685
Interest rate swaps, options and forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	13,104
OTC derivative assets having maturity period of 1 to 5 years	96,631
OTC derivative assets having maturity period of greater than 5 years	95,973
OTC derivative assets cross-maturity netting	(91,673)
Total OTC derivative assets, net of cross-maturity netting	114,035
OTC derivative liabilities having maturity period of 0 to 12 months	16,388
OTC derivative liabilities having maturity period of 1 to 5 years	148,685
OTC derivative liabilities having maturity period of greater than 5 years	198,569
OTC derivative liabilities cross-maturity netting	(91,673)
Total OTC derivative liabilities, net of cross-maturity netting	$ 271,969