Fair Value Disclosures - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Nov. 30, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other secured financings	$ 860,602,000		$ 605,824,000
Transfers of assets from Level 2 to Level 3	205,200,000	91,000,000
Transfers of assets from Level 3 to Level 2	110,300,000	47,300,000
Transfers of liabilities from Level 2 to Level 3		4,800,000
Net gains/(losses) on Level 3 assets (realized and unrealized)	(49,700,000)	20,300,000
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(6,900,000)	800,000
Transfers of liabilities from Level 3 to Level 2	3,000,000	2,900,000
Unadjusted net asset value of the funds	216,200,000		180,000,000
Unadjusted net liability value of the funds	0		300,000
Aggregate fair value of loans and other receivables	14,100,000		0
Loan and other receivables on nonaccrual status	285,700,000		274,600,000
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other secured financings	5,600,000		7,800,000
Derivative liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of liabilities from Level 3 to Level 2		3,400,000
Corporate debt securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3	2,400,000	7,400,000
Transfers of assets from Level 3 to Level 2	25,600,000	200,000
Corporate equity securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3	1,700,000	2,300,000
Transfers of assets from Level 3 to Level 2	4,400,000	3,600,000
Collateralized debt obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Transfers of assets from Level 2 to Level 3	64,500,000	23,500,000
Transfers of assets from Level 3 to Level 2	34,300,000	7,900,000
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	35,300,000	38,100,000
Transfers of assets from Level 3 to Level 2	35,700,000	19,100,000
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	10,300,000	9,000,000
Transfers of assets from Level 3 to Level 2	4,500,000	200,000
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	5,000,000	1,800,000
Transfers of assets from Level 3 to Level 2		12,200,000
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	16,400,000	8,900,000
Transfers of assets from Level 3 to Level 2	5,700,000	3,300,000
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	69,200,000
Transfers of assets from Level 3 to Level 2		$ 800,000
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% 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%
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