Fair Value Disclosures - Additional Information (Details) - USD ($)	12 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	$ 58,400,000	$ 57,800,000	$ 33,800,000
Transfers of assets from Level 3 to Level 2	26,700,000	12,300,000	60,400,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(27,100,000)	(12,700,000)	(24,600,000)
Net gains (losses) on Level 3 liabilities (realized and unrealized)	44,500,000	33,600,000	1,700,000
Value of asset excluded from significant unobservable inputs	31,900,000	11,100,000
Value of liability excluded from significant unobservable inputs	400,000	500,000
Aggregate fair value of loans and other receivables on nonaccrual status and/or 90 days or greater past due	127,000,000.0	105,300,000
Loan and other receivables greater than 90 days past due	24,800,000	19,400,000
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	796,797,000	707,960,000
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	27,400,000
Transfers of assets from Level 3 to Level 2	8,600,000		40,900,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(5,505,000)	(5,137,000)	24,794,000
Other ABS
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	12,100,000
Transfers of assets from Level 3 to Level 2	2,600,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	433,000	(9,934,000)	(17,705,000)
Corporate debt securities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	8,900,000		8,300,000
Transfers of assets from Level 3 to Level 2		3,600,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(4,860,000)	(439,000)	(3,723,000)
Net gains (losses) on Level 3 liabilities (realized and unrealized)	381,000	0	1,000
CMBS
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	5,600,000	16,300,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(2,888,000)	(2,186,000)	(5,346,000)
Net gains (losses) on Level 3 liabilities (realized and unrealized)	(35,000)	105,000	(105,000)
CDOs and CLOs
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	3,000,000.0	17,300,000
Transfers of assets from Level 3 to Level 2	8,800,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(2,342,000)	(14,368,000)	(19,858,000)
Corporate equity securities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 3 to Level 2	6,000,000.0	2,900,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(10,380,000)	24,023,000	3,262,000
Net gains (losses) on Level 3 liabilities (realized and unrealized)	2,649,000	0	(60,000)
Net derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	57,200,000
Transfers of liabilities from Level 3 to Level 2	14,300,000
Net gains (losses) on Level 3 liabilities (realized and unrealized)	21,452,000	3,237,000	1,638,000
Structured notes
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	22,600,000	146,200,000
Transfers of liabilities from Level 3 to Level 2	61,700,000
RMBS
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		15,300,000	19,600,000
Transfers of assets from Level 3 to Level 2		4,600,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(1,669,000)	(6,970,000)	(10,817,000)
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	35,000,000.0	34,800,000
Nonrecurring | Level 1
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value on a non-recurring basis	0	0	0
Liabilities measured at fair value on a non-recurring basis	$ 0	$ 0	$ 0