Fair Value Disclosures - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2020	Aug. 31, 2019	Nov. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	$ 64,500	$ 79,000	$ 132,000	$ 60,200
Transfers of assets from Level 3 to Level 2	39,900	69,400	22,300	47,800
Transfers of liabilities from Level 2 to Level 3	54,400	43,500	37,300	98,300
Transfers of liabilities from Level 3 to Level 2	30,000	23,800	106,200	64,100
Net gains/(losses) on Level 3 assets (realized and unrealized)	7,200	(6,900)	(58,100)	(200)
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(124,300)	12,800	50,100	55,800
Aggregate fair value of loans and other receivables on nonaccrual status and/or 90 days or greater past due	162,600		162,600		$ 127,000
Loans and other receivables greater than 90 days past due	13,300		13,300		24,800
Cash and securities segregated and on deposit for regulatory purposes with clearing and depository organizations	986,117		986,117		796,797
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	31,800	23,700	13,400	30,600
Transfers of assets from Level 3 to Level 2	7,400	36,000	9,200	9,200
Transfers of liabilities from Level 2 to Level 3		13,300
Net gains/(losses) on Level 3 assets (realized and unrealized)	8,302	(2,847)	(7,093)	3,933
CDOs and CLOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	19,500		34,100
Transfers of assets from Level 3 to Level 2	8,900
Net gains/(losses) on Level 3 assets (realized and unrealized)	3,796	(1,514)	(8,651)	(5,892)
Other ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	5,800		23,500	10,800
Transfers of assets from Level 3 to Level 2	22,900		5,600	10,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(1,585)	(1,689)	(3,495)	(929)
RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	5,500
Net gains/(losses) on Level 3 assets (realized and unrealized)	1,240	(1,917)	(1,347)	(2,573)
Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	50,100
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(6,636)	520	(2,986)	1,342
Net derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	4,100	17,600	35,200	64,500
Transfers of liabilities from Level 3 to Level 2	25,600		45,000
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	12,175	19,519	63,367	48,746
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)	(3,257)	(6,407)	(33,753)	(3,971)
Corporate equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3			36,600
Transfers of assets from Level 3 to Level 2		22,100	3,100	14,800
Net gains/(losses) on Level 3 assets (realized and unrealized)	(588)	12,542	(3,793)	16,381
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	12	(401)	(258)	(401)
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	3,000	21,600	60,700	61,700
Corporate debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3			18,600	10,500
Net gains/(losses) on Level 3 assets (realized and unrealized)	(889)	(3,072)	(162)	(4,904)
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	15	$ 650	261	$ 867
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	$ 55,900		$ 55,900		$ 35,000