Fair Value Disclosures - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	May 31, 2019	May 31, 2018	May 31, 2019	May 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	$ 31,700	$ 78,700	$ 42,300	$ 49,100
Transfers of assets from Level 3 to Level 2	79,500	28,000	89,000	14,900
Transfers of liabilities from Level 2 to Level 3	57,400		69,600
Transfers of liabilities from Level 3 to Level 2	105,400		63,200
Net gains/(losses) on Level 3 assets (realized and unrealized)	2,000	(17,900)	2,700	(900)
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	14,100	25,800	42,800	27,600
Aggregate fair value of loans and other receivables on nonaccrual status and/or 90 days or greater past due	119,500		119,500		$ 105,300
Loans and other receivables greater than 90 days past due	65,200		65,200		19,400
Cash and securities segregated and on deposit for regulatory purposes with clearing and depository organizations	543,429		543,429		707,960
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	11,300	16,400	15,700
Transfers of assets from Level 3 to Level 2	10,500	9,200
Net gains/(losses) on Level 3 assets (realized and unrealized)	(2,753)	(6,051)	2,434	(201)
Investments at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 3 to Level 2	39,800		40,200
Net gains/(losses) on Level 3 assets (realized and unrealized)	2,841	(82)	(1,162)	418
CDOs and CLOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		20,300		12,700
Transfers of assets from Level 3 to Level 2	17,600	11,700	12,500
Net gains/(losses) on Level 3 assets (realized and unrealized)	(1,793)	(2,350)	(2,790)	(2,961)
Net derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	41,500		58,700
Transfers of liabilities from Level 3 to Level 2	14,400
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(14,760)	(1,580)	(29,079)	(668)
Structured Notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3	9,500		10,300
Transfers of liabilities from Level 3 to Level 2	91,000		52,300
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		17,100		19,700
Net gains/(losses) on Level 3 assets (realized and unrealized)	(357)	(2,213)	(180)	(2,292)
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(70)	(35)		(105)
Other ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	7,600	15,900	10,800
Transfers of assets from Level 3 to Level 2			22,300
Net gains/(losses) on Level 3 assets (realized and unrealized)	3,070	(4,001)	(1,014)	(5,476)
RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 3 to Level 2				9,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(802)	(5,416)	(316)	(4,193)
Long-term debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 2 to Level 3		158,102		107,424
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	1,163	$ (20,838)	(12,854)	$ (28,082)
US Treasury Securities | Level 1
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	$ 34,800		$ 34,800		$ 34,800