Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Details) $ in Thousands	May 31, 2020 USD ($)
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	$ 255,519
OTC derivative assets having maturity period of 1 to 5 years	318,940
OTC derivative assets having maturity period of greater than 5 years	271,928
OTC derivative assets cross-maturity netting	(64,997)
Total OTC derivative assets, net of cross-maturity netting	781,390
Cross product counterparty netting	(37,469)
Total OTC derivative assets included in Financial instruments owned	743,921
OTC derivative liabilities having maturity period of 0 to 12 months	179,506
OTC derivative liabilities having maturity period of 1 to 5 years	403,210
OTC derivative liabilities having maturity period of greater than 5 years	182,196
OTC derivative liabilities cross-maturity netting	(64,997)
Total OTC derivative liabilities, net of cross-maturity netting	699,915
Cross product counterparty netting	(37,469)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	662,446
Exchange traded derivative assets, with fair value	34,100
Cash collateral received	192,600
Exchange traded derivative liabilities, with fair value	102,400
Cash collateral pledged	347,100
Equity forwards, swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	46,129
OTC derivative assets having maturity period of 1 to 5 years	200
OTC derivative assets having maturity period of greater than 5 years	18,280
OTC derivative assets cross-maturity netting	(13,218)
Total OTC derivative assets, net of cross-maturity netting	51,391
OTC derivative liabilities having maturity period of 0 to 12 months	14,944
OTC derivative liabilities having maturity period of 1 to 5 years	251,025
OTC derivative liabilities having maturity period of greater than 5 years	101,362
OTC derivative liabilities cross-maturity netting	(13,218)
Total OTC derivative liabilities, net of cross-maturity netting	354,113
Credit default swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	11
OTC derivative assets having maturity period of 1 to 5 years	900
OTC derivative assets having maturity period of greater than 5 years	133
OTC derivative assets cross-maturity netting	(11)
Total OTC derivative assets, net of cross-maturity netting	1,033
OTC derivative liabilities having maturity period of 0 to 12 months	0
OTC derivative liabilities having maturity period of 1 to 5 years	1,489
OTC derivative liabilities having maturity period of greater than 5 years	69
OTC derivative liabilities cross-maturity netting	(11)
Total OTC derivative liabilities, net of cross-maturity netting	1,547
Total return swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	83,333
OTC derivative assets having maturity period of 1 to 5 years	63,660
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(8,838)
Total OTC derivative assets, net of cross-maturity netting	138,155
OTC derivative liabilities having maturity period of 0 to 12 months	61,841
OTC derivative liabilities having maturity period of 1 to 5 years	56,238
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(8,838)
Total OTC derivative liabilities, net of cross-maturity netting	109,241
Foreign currency forwards, swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	55,197
OTC derivative assets having maturity period of 1 to 5 years	11,655
OTC derivative assets having maturity period of greater than 5 years	113
OTC derivative assets cross-maturity netting	(6,611)
Total OTC derivative assets, net of cross-maturity netting	60,354
OTC derivative liabilities having maturity period of 0 to 12 months	74,272
OTC derivative liabilities having maturity period of 1 to 5 years	10,196
OTC derivative liabilities having maturity period of greater than 5 years	92
OTC derivative liabilities cross-maturity netting	(6,611)
Total OTC derivative liabilities, net of cross-maturity netting	77,949
Interest rate swaps, options and forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	70,849
OTC derivative assets having maturity period of 1 to 5 years	242,525
OTC derivative assets having maturity period of greater than 5 years	253,402
OTC derivative assets cross-maturity netting	(36,319)
Total OTC derivative assets, net of cross-maturity netting	530,457
OTC derivative liabilities having maturity period of 0 to 12 months	28,449
OTC derivative liabilities having maturity period of 1 to 5 years	84,262
OTC derivative liabilities having maturity period of greater than 5 years	80,673
OTC derivative liabilities cross-maturity netting	(36,319)
Total OTC derivative liabilities, net of cross-maturity netting	$ 157,065