Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Detail) $ in Thousands	May 31, 2019 USD ($)
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	$ 179,010
OTC derivative assets having maturity period of 1 to 5 years	243,900
OTC derivative assets having maturity period of greater than 5 years	124,949
OTC derivative assets cross-maturity netting	(90,323)
Total OTC derivative assets, net of cross-maturity netting	457,536
Cross product counterparty netting	(39,313)
Total OTC derivative assets included in Financial instruments owned	418,223
OTC derivative liabilities having maturity period of 0 to 12 months	232,537
OTC derivative liabilities having maturity period of 1 to 5 years	257,629
OTC derivative liabilities having maturity period of greater than 5 years	161,590
OTC derivative liabilities cross-maturity netting	(90,323)
Total OTC derivative liabilities, net of cross-maturity netting	561,433
Cross product counterparty netting	(39,313)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	522,120
Exchange traded derivative assets	22,300
Cash collateral received	117,100
Exchange traded derivative liabilities, with fair value	321,400
Cash collateral pledged	289,300
Equity swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	40,703
OTC derivative assets having maturity period of 1 to 5 years	26
OTC derivative assets having maturity period of greater than 5 years	4,031
OTC derivative assets cross-maturity netting	(2,233)
Total OTC derivative assets, net of cross-maturity netting	42,527
OTC derivative liabilities having maturity period of 0 to 12 months	28,465
OTC derivative liabilities having maturity period of 1 to 5 years	118,560
OTC derivative liabilities having maturity period of greater than 5 years	40,591
OTC derivative liabilities cross-maturity netting	(2,233)
Total OTC derivative liabilities, net of cross-maturity netting	185,383
Credit default swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	807
OTC derivative assets having maturity period of 1 to 5 years	966
OTC derivative assets having maturity period of greater than 5 years	2,294
OTC derivative assets cross-maturity netting	(469)
Total OTC derivative assets, net of cross-maturity netting	3,598
OTC derivative liabilities having maturity period of 0 to 12 months	40
OTC derivative liabilities having maturity period of 1 to 5 years	2,535
OTC derivative liabilities having maturity period of greater than 5 years	3,583
OTC derivative liabilities cross-maturity netting	(469)
Total OTC derivative liabilities, net of cross-maturity netting	5,689
Total return swaps
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	9,675
OTC derivative assets having maturity period of 1 to 5 years	51,481
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(1,607)
Total OTC derivative assets, net of cross-maturity netting	59,549
OTC derivative liabilities having maturity period of 0 to 12 months	89,603
OTC derivative liabilities having maturity period of 1 to 5 years	37,003
OTC derivative liabilities having maturity period of greater than 5 years	0
OTC derivative liabilities cross-maturity netting	(1,607)
Total OTC derivative liabilities, net of cross-maturity netting	124,999
Foreign currency forwards, swaps and options
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	52,486
OTC derivative assets having maturity period of 1 to 5 years	21,850
OTC derivative assets having maturity period of greater than 5 years	0
OTC derivative assets cross-maturity netting	(15,480)
Total OTC derivative assets, net of cross-maturity netting	58,856
OTC derivative liabilities having maturity period of 0 to 12 months	67,386
OTC derivative liabilities having maturity period of 1 to 5 years	18,225
OTC derivative liabilities having maturity period of greater than 5 years	1,404
OTC derivative liabilities cross-maturity netting	(15,480)
Total OTC derivative liabilities, net of cross-maturity netting	71,535
Fixed income forwards
Derivative [Line Items]
OTC derivative liabilities having maturity period of 0 to 12 months	600
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	600
Interest rate swaps, options and forwards
Derivative [Line Items]
OTC derivative assets having maturity period of 0 to 12 months	75,339
OTC derivative assets having maturity period of 1 to 5 years	169,577
OTC derivative assets having maturity period of greater than 5 years	118,624
OTC derivative assets cross-maturity netting	(70,534)
Total OTC derivative assets, net of cross-maturity netting	293,006
OTC derivative liabilities having maturity period of 0 to 12 months	46,443
OTC derivative liabilities having maturity period of 1 to 5 years	81,306
OTC derivative liabilities having maturity period of greater than 5 years	116,012
OTC derivative liabilities cross-maturity netting	(70,534)
Total OTC derivative liabilities, net of cross-maturity netting	$ 173,227