Fair Value Disclosures - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 31, 2015	Aug. 31, 2014	Aug. 31, 2015	Aug. 31, 2014	Nov. 30, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Investments at fair value	$ 40,200,000		$ 40,200,000		$ 42,200,000
Other secured financings	806,634,000		806,634,000		605,824,000
Transfers of assets from Level 2 to Level 3	73,400,000	$ 87,800,000	157,700,000	$ 79,300,000
Transfers of assets from Level 3 to Level 2	91,400,000	108,600,000	88,100,000	68,100,000
Transfers of liabilities from Level 3 to Level 2		8,600,000		3,900,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	64,900,000	(6,000,000)	48,500,000	19,100,000
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	1,700,000	4,200,000	(2,300,000)	(2,000,000)
Unadjusted net asset value of the funds			120,800,000		137,800,000
Unadjusted net liability value of the funds			800,000		300,000
Aggregate fair value of loans and other receivables	13,000,000		13,000,000		0
Loan and other receivables on nonaccrual status	313,900,000		313,900,000		274,600,000
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other secured financings	0		0		$ 7,800,000
Loan Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of liabilities from Level 2 to Level 3	2,500,000
Other Secured Financings [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of liabilities from Level 3 to Level 2	51,600,000		51,600,000
Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3	5,000,000		12,200,000
Transfers of assets from Level 3 to Level 2				8,000,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(5,276,000)	5,454,000	(5,425,000)	10,727,000
Derivative liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of liabilities from Level 3 to Level 2				3,300,000
Corporate equity securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3			1,600,000
Transfers of assets from Level 3 to Level 2	1,900,000	13,900,000	11,800,000	6,500,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	3,901,000	(480,000)	10,247,000	(1,528,000)
Collateralized debt obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3	42,800,000	15,200,000	16,000,000	7,500,000
Transfers of assets from Level 3 to Level 2	39,900,000	5,300,000	25,600,000	1,300,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(12,560,000)	(845,000)	(28,999,000)	5,198,000
Residential mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3	17,800,000	30,100,000	21,300,000	27,200,000
Transfers of assets from Level 3 to Level 2	18,500,000	12,500,000	15,900,000	23,100,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(3,009,000)	(2,557,000)	(6,776,000)	(6,974,000)
Commercial mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3	3,700,000	6,800,000	9,800,000	4,600,000
Transfers of assets from Level 3 to Level 2	5,200,000	5,000,000	5,600,000	500,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(510,000)	(256,000)	(2,053,000)	(3,120,000)
Other asset-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3		1,500,000	1,400,000	1,300,000
Transfers of assets from Level 3 to Level 2		38,600,000		3,500,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	870,000	1,272,000	666,000	256,000
Loans and other receivables [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3	4,100,000	25,100,000	19,200,000	31,400,000
Transfers of assets from Level 3 to Level 2	3,500,000	25,100,000	6,100,000	18,000,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(2,111,000)	(8,074,000)	(7,331,000)	(9,028,000)
Investments at fair value [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3		5,400,000	76,200,000	6,500,000
Transfers of assets from Level 3 to Level 2	21,000,000		22,700,000	7,200,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	$ 83,580,000	$ (512,000)	$ 88,195,000	$ 23,615,000
3.875% Convertible Senior Debentures due 2029 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Debt instrument interest rate	3.875%		3.875%
3.875% Convertible Senior Debentures due 2029 [Member] | Leucadia [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Debt instrument interest rate	3.875%		3.875%
Debt instrument maturity year			Nov. 01, 2029
Volatility curve used in valuing embedded option			252 days
Embedded conversion option [Member] | Leucadia [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Debt instrument maturity year			Nov. 01, 2017