Derivative Financial Instruments - Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities (Details) $ in Thousands	Feb. 28, 2021 USD ($)
OTC Derivative Assets [Abstract]
0 – 12 Months	$ 410,215
1 – 5 Years	170,559
Greater Than 5 Years	167,823
OTC derivative assets cross-maturity netting	(59,603)
Total OTC derivative assets, net of cross-maturity netting	688,994
Cross product counterparty netting	(24,263)
Total OTC derivative assets included in Financial instruments owned	664,731
OTC Derivative Liabilities [Abstract]
0 – 12 Months	432,273
1 – 5 Years	973,701
Greater Than 5 Years	259,591
OTC derivative liabilities cross-maturity netting	(59,603)
Total OTC derivative liabilities, net of cross-maturity netting	1,605,962
Cross product counterparty netting	(24,263)
Total OTC derivative liabilities included in Financial instruments sold, not yet purchased	1,581,699
Exchange traded derivative assets, with fair value	61,400
Cash collateral received	196,200
Exchange traded derivative liabilities, with fair value	91,900
Cash collateral pledged	588,700
Equity options and forwards
OTC Derivative Assets [Abstract]
0 – 12 Months	29,936
1 – 5 Years	1,526
Greater Than 5 Years	13,544
OTC derivative assets cross-maturity netting	(20,365)
Total OTC derivative assets, net of cross-maturity netting	24,641
OTC Derivative Liabilities [Abstract]
0 – 12 Months	19,834
1 – 5 Years	522,218
Greater Than 5 Years	143,586
OTC derivative liabilities cross-maturity netting	(20,365)
Total OTC derivative liabilities, net of cross-maturity netting	665,273
Credit default swaps
OTC Derivative Assets [Abstract]
0 – 12 Months	2
1 – 5 Years	759
Greater Than 5 Years	0
OTC derivative assets cross-maturity netting	0
Total OTC derivative assets, net of cross-maturity netting	761
OTC Derivative Liabilities [Abstract]
0 – 12 Months	20
1 – 5 Years	3,530
Greater Than 5 Years	0
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	3,550
Total return swaps
OTC Derivative Assets [Abstract]
0 – 12 Months	130,651
1 – 5 Years	16,711
Greater Than 5 Years	0
OTC derivative assets cross-maturity netting	(4,147)
Total OTC derivative assets, net of cross-maturity netting	143,215
OTC Derivative Liabilities [Abstract]
0 – 12 Months	152,604
1 – 5 Years	382,556
Greater Than 5 Years	1,641
OTC derivative liabilities cross-maturity netting	(4,147)
Total OTC derivative liabilities, net of cross-maturity netting	532,654
Foreign currency forwards, swaps and options
OTC Derivative Assets [Abstract]
0 – 12 Months	85,919
1 – 5 Years	13,318
Greater Than 5 Years	0
OTC derivative assets cross-maturity netting	(5,524)
Total OTC derivative assets, net of cross-maturity netting	93,713
OTC Derivative Liabilities [Abstract]
0 – 12 Months	114,279
1 – 5 Years	8,811
Greater Than 5 Years	0
OTC derivative liabilities cross-maturity netting	(5,524)
Total OTC derivative liabilities, net of cross-maturity netting	117,566
Fixed income forwards
OTC Derivative Liabilities [Abstract]
0 – 12 Months	5,359
1 – 5 Years	0
Greater Than 5 Years	0
OTC derivative liabilities cross-maturity netting	0
Total OTC derivative liabilities, net of cross-maturity netting	5,359
Interest rate swaps, options and forwards
OTC Derivative Assets [Abstract]
0 – 12 Months	163,707
1 – 5 Years	138,245
Greater Than 5 Years	154,279
OTC derivative assets cross-maturity netting	(29,567)
Total OTC derivative assets, net of cross-maturity netting	426,664
OTC Derivative Liabilities [Abstract]
0 – 12 Months	140,177
1 – 5 Years	56,586
Greater Than 5 Years	114,364
OTC derivative liabilities cross-maturity netting	(29,567)
Total OTC derivative liabilities, net of cross-maturity netting	$ 281,560