Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Details) $ in Thousands	Aug. 31, 2020 USD ($)
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	$ 254,886
OTC derivative assets having maturity period of 1 to 5 years	297,738
OTC derivative assets having maturity period of greater than 5 years	240,514
OTC derivative assets cross-maturity netting	(89,613)
Total OTC derivative assets, net of cross-maturity netting	703,525
Cross product counterparty netting	(22,759)
Total OTC derivative assets included in Financial instruments owned	680,766
OTC derivative liabilities having maturity period of 0 to 12 months	173,340
OTC derivative liabilities having maturity period of 1 to 5 years	567,851
OTC derivative liabilities having maturity period of greater than 5 years	229,335
OTC derivative liabilities cross-maturity netting	(89,613)
Total OTC derivative liabilities, net of cross-maturity netting	880,913
Cross product counterparty netting	(22,759)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	858,154
Exchange traded derivative assets, with fair value	25,100
Cash collateral received	201,600
Exchange traded derivative liabilities, with fair value	14,500
Cash collateral pledged	389,500
Equity options and forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	21,437
OTC derivative assets having maturity period of 1 to 5 years	44,672
OTC derivative assets having maturity period of greater than 5 years	15,160
OTC derivative assets cross-maturity netting	(25,445)
Total OTC derivative assets, net of cross-maturity netting	55,824
OTC derivative liabilities having maturity period of 0 to 12 months	15,474
OTC derivative liabilities having maturity period of 1 to 5 years	370,915
OTC derivative liabilities having maturity period of greater than 5 years	156,839
OTC derivative liabilities cross-maturity netting	(25,445)
Total OTC derivative liabilities, net of cross-maturity netting	517,783
Credit default swaps
Derivative [Line Items]
OTC derivative liabilities having maturity period of 0 to 12 months	12
OTC derivative liabilities having maturity period of 1 to 5 years	1,108
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	1,120
Total return swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	74,923
OTC derivative assets having maturity period of 1 to 5 years	19,764
OTC derivative assets having maturity period of greater than 5 years	2,872
OTC derivative assets cross-maturity netting	(14,666)
Total OTC derivative assets, net of cross-maturity netting	82,893
OTC derivative liabilities having maturity period of 0 to 12 months	58,888
OTC derivative liabilities having maturity period of 1 to 5 years	103,567
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(14,666)
Total OTC derivative liabilities, net of cross-maturity netting	147,789
Foreign currency forwards, swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	63,570
OTC derivative assets having maturity period of 1 to 5 years	28,993
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(4,477)
Total OTC derivative assets, net of cross-maturity netting	88,086
OTC derivative liabilities having maturity period of 0 to 12 months	55,430
OTC derivative liabilities having maturity period of 1 to 5 years	11,792
OTC derivative liabilities having maturity period of greater than 5 years	34
OTC derivative liabilities cross-maturity netting	(4,477)
Total OTC derivative liabilities, net of cross-maturity netting	62,779
Fixed income forwards
Derivative [Line Items]
OTC derivative liabilities having maturity period of 0 to 12 months	1,404
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	1,404
Interest rate swaps, options and forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	94,956
OTC derivative assets having maturity period of 1 to 5 years	204,309
OTC derivative assets having maturity period of greater than 5 years	222,482
OTC derivative assets cross-maturity netting	(45,025)
Total OTC derivative assets, net of cross-maturity netting	476,722
OTC derivative liabilities having maturity period of 0 to 12 months	42,132
OTC derivative liabilities having maturity period of 1 to 5 years	80,469
OTC derivative liabilities having maturity period of greater than 5 years	72,462
OTC derivative liabilities cross-maturity netting	(45,025)
Total OTC derivative liabilities, net of cross-maturity netting	$ 150,038