Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Details) $ in Thousands	Feb. 29, 2020 USD ($)
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	$ 344,638
OTC derivative assets having maturity period of 1 to 5 years	259,023
OTC derivative assets having maturity period of greater than 5 years	243,819
OTC derivative assets cross-maturity netting	(68,677)
Total OTC derivative assets, net of cross-maturity netting	778,803
Cross product counterparty netting	(15,399)
Total OTC derivative assets included in Financial instruments owned	763,404
OTC derivative liabilities having maturity period of 0 to 12 months	291,421
OTC derivative liabilities having maturity period of 1 to 5 years	376,062
OTC derivative liabilities having maturity period of greater than 5 years	191,973
OTC derivative liabilities cross-maturity netting	(68,677)
Total OTC derivative liabilities, net of cross-maturity netting	790,779
Cross product counterparty netting	(15,399)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	775,380
Exchange traded derivative assets, with fair value	74,500
Cash collateral received	240,300
Exchange traded derivative liabilities, with fair value	292,100
Cash collateral pledged	372,100
Equity forwards, swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	28,521
OTC derivative assets having maturity period of 1 to 5 years	7,516
OTC derivative assets having maturity period of greater than 5 years	6,959
OTC derivative assets cross-maturity netting	(12,901)
Total OTC derivative assets, net of cross-maturity netting	30,095
OTC derivative liabilities having maturity period of 0 to 12 months	35,005
OTC derivative liabilities having maturity period of 1 to 5 years	193,428
OTC derivative liabilities having maturity period of greater than 5 years	80,442
OTC derivative liabilities cross-maturity netting	(12,901)
Total OTC derivative liabilities, net of cross-maturity netting	295,974
Credit default swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	31
OTC derivative assets having maturity period of 1 to 5 years	4,079
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	4,072
OTC derivative liabilities having maturity period of 0 to 12 months	1,401
OTC derivative liabilities having maturity period of 1 to 5 years	2,539
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	3,902
Total return swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	160,829
OTC derivative assets having maturity period of 1 to 5 years	37,825
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(11,543)
Total OTC derivative assets, net of cross-maturity netting	187,111
OTC derivative liabilities having maturity period of 0 to 12 months	140,657
OTC derivative liabilities having maturity period of 1 to 5 years	71,668
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(11,543)
Total OTC derivative liabilities, net of cross-maturity netting	200,782
Foreign currency forwards, swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	66,282
OTC derivative assets having maturity period of 1 to 5 years	3,757
OTC derivative assets having maturity period of greater than 5 years	3
OTC derivative assets cross-maturity netting	(3,005)
Total OTC derivative assets, net of cross-maturity netting	67,037
OTC derivative liabilities having maturity period of 0 to 12 months	67,858
OTC derivative liabilities having maturity period of 1 to 5 years	2,861
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(3,005)
Total OTC derivative liabilities, net of cross-maturity netting	67,714
Fixed income forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	8,847
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	8,847
OTC derivative liabilities having maturity period of 0 to 12 months	581
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	581
Interest rate swaps, options and forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	80,128
OTC derivative assets having maturity period of 1 to 5 years	205,846
OTC derivative assets having maturity period of greater than 5 years	236,857
OTC derivative assets cross-maturity netting	(41,190)
Total OTC derivative assets, net of cross-maturity netting	481,641
OTC derivative liabilities having maturity period of 0 to 12 months	45,919
OTC derivative liabilities having maturity period of 1 to 5 years	105,566
OTC derivative liabilities having maturity period of greater than 5 years	111,531
OTC derivative liabilities cross-maturity netting	(41,190)
Total OTC derivative liabilities, net of cross-maturity netting	$ 221,826