Fair Value Disclosures - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2019	Aug. 31, 2018	Nov. 30, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	$ 79,000	$ 13,600	$ 60,200	$ 49,100
Transfers of assets from Level 3 to Level 2	69,400	13,800	47,800	10,000
Transfers of liabilities from Level 2 to Level 3	43,500		98,300
Transfers of liabilities from Level 3 to Level 2	23,800		64,100
Net gains/(losses) on Level 3 assets (realized and unrealized)	(6,900)	9,800	(200)	10,400
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	12,800	(4,400)	55,800	26,800
Aggregate fair value of loans and other receivables on nonaccrual status and/or 90 days or greater past due	113,400		113,400		$ 105,300
Loans and other receivables greater than 90 days past due	31,900		31,900		19,400
Cash and securities segregated and on deposit for regulatory purposes with clearing and depository organizations	658,335		658,335		707,960
Investments at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	35,100
Transfers of assets from Level 3 to Level 2			8,600
Net gains/(losses) on Level 3 assets (realized and unrealized)	(6,407)	0	(3,971)	417
Loans and other receivables
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	23,700		30,600	15,300
Transfers of assets from Level 3 to Level 2	36,000		9,200
Net gains/(losses) on Level 3 assets (realized and unrealized)	(2,847)	(1,353)	3,933	(2,812)
Corporate equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 3 to Level 2	22,100	2,600	14,800	2,500
Net gains/(losses) on Level 3 assets (realized and unrealized)	12,542	12,128	16,381	30,098
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	401	326	401	365
Corporate debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3			10,500
Net gains/(losses) on Level 3 assets (realized and unrealized)	(3,072)	1,057	(4,904)	1,090
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(650)	39	(867)	39
Net derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	17,600		64,500
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(19,519)	1,107	(48,746)	(1,034)
Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	13,300
Structured Notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	11,000		20,800
Transfers of liabilities from Level 3 to Level 2	21,600		61,700
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		2,600		17,000
Transfers of assets from Level 3 to Level 2		4,600
Net gains/(losses) on Level 3 assets (realized and unrealized)	(2,003)	(222)	(2,196)	(1,236)
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	0	70	0	(35)
CDOs and CLOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3				8,700
Transfers of assets from Level 3 to Level 2		3,700
Net gains/(losses) on Level 3 assets (realized and unrealized)	(1,514)	567	(5,892)	(2,323)
Other ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		3,900	10,800
Transfers of assets from Level 3 to Level 2			10,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(1,689)	(2,269)	(929)	(7,528)
RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		2,900
Transfers of assets from Level 3 to Level 2				4,600
Net gains/(losses) on Level 3 assets (realized and unrealized)	(1,917)	(66)	(2,573)	(7,334)
Long-term debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3		0		107,424
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	7,455	$ 3,004	(5,286)	$ (25,078)
US Treasury Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash and securities segregated and on deposit for regulatory purposes with clearing and depository organizations	$ 35,000		$ 35,000		$ 34,800