Fair Value Disclosures - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Nov. 30, 2020	Nov. 30, 2019	Nov. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	$ 88,000	$ 58,400	$ 57,800
Transfers of assets from Level 3 to Level 2	24,700	26,700	12,300
Transfers of liabilities from Level 2 to Level 3	1,900
Transfers of liabilities from Level 3 to Level 2	143,400
Net gains/(losses) on Level 3 assets (realized and unrealized)	(55,100)	(27,100)	12,700
Net gains (losses) on Level 3 liabilities (realized and unrealized)	(82,100)	44,500	33,600
Value of asset excluded from significant unobservable inputs	17,300	31,900
Value of liability excluded from significant unobservable inputs	(800)	400
Aggregate fair value of loans and other receivables on nonaccrual status and/or 90 days or greater past due	69,700	127,000
Loan and other receivables greater than 90 days past due	3,800	24,800
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	604,321	796,797
CDOs and CLOs
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		3,000	17,300
Transfers of assets from Level 3 to Level 2		8,800
Net gains/(losses) on Level 3 assets (realized and unrealized)	(5,703)	(2,342)	(14,368)
CMBS
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		5,600	16,300
Net gains/(losses) on Level 3 assets (realized and unrealized)	(827)	(2,888)	(2,186)
Net gains (losses) on Level 3 liabilities (realized and unrealized)	0	(35)	105
RMBS
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3			15,300
Transfers of assets from Level 3 to Level 2			4,600
Net gains/(losses) on Level 3 assets (realized and unrealized)	(934)	(1,669)	(6,970)
Corporate debt securities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	18,000
Transfers of assets from Level 3 to Level 2	3,000		3,600
Net gains/(losses) on Level 3 assets (realized and unrealized)	83	(4,860)	(439)
Net gains (losses) on Level 3 liabilities (realized and unrealized)	268	381	0
Corporate equity securities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	32,500	8,900
Transfers of assets from Level 3 to Level 2	5,100	6,000	2,900
Net gains/(losses) on Level 3 assets (realized and unrealized)	(3,961)	(10,380)	24,023
Net gains (losses) on Level 3 liabilities (realized and unrealized)	(456)	2,649	0
Structured notes
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3		22,600	146,200
Transfers of liabilities from Level 3 to Level 2	80,600	61,700
Loans and other receivables
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	10,900	27,400
Transfers of assets from Level 3 to Level 2	7,100	8,600
Net gains/(losses) on Level 3 assets (realized and unrealized)	(20,487)	(5,505)	(5,137)
Other ABS
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	23,000	12,100
Transfers of assets from Level 3 to Level 2	6,800	2,600
Net gains/(losses) on Level 3 assets (realized and unrealized)	(3,848)	433	(9,934)
Derivatives, liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3		57,200
Transfers of liabilities from Level 3 to Level 2	60,800	14,300
Net gains (losses) on Level 3 liabilities (realized and unrealized)	40	21,452	3,237
US Treasury securities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	34,200	35,000
Loans
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	1,800
Net gains (losses) on Level 3 liabilities (realized and unrealized)	$ 520	$ 1,382	$ (84)