Investments - Additional Information (Detail) (USD $)	3 Months Ended				3 Months Ended				3 Months Ended		12 Months Ended			3 Months Ended			12 Months Ended
	Feb. 28, 2013 Y D	Feb. 29, 2012	Nov. 30, 2012	Feb. 28, 2011	Feb. 28, 2013 Secured Revolving Credit Facility [Member]	Feb. 28, 2013 Jefferies Finance, LLC [Member]	Feb. 29, 2012 Jefferies Finance, LLC [Member]	Nov. 30, 2012 Jefferies Finance, LLC [Member]	Feb. 28, 2013 Jefferies LoanCore, LLC [Member]	Feb. 29, 2012 Jefferies LoanCore, LLC [Member]	Nov. 30, 2012 Jefferies LoanCore, LLC [Member]	Mar. 31, 2013 Subsequent event [Member] Jefferies Finance, LLC [Member]	Mar. 19, 2013 Subsequent event [Member] Jefferies Finance, LLC [Member]	Mar. 19, 2013 Subsequent event [Member] Jefferies Finance, LLC [Member] Secured Revolving Credit Facility [Member]	Feb. 28, 2013 Knight Capital Group, Inc. [Member]	Dec. 31, 2012 Knight Capital Group, Inc. [Member]	Dec. 31, 2012 Knight Capital Group, Inc. [Member]	Aug. 06, 2012 Knight Capital Group, Inc. [Member]	Aug. 06, 2012 Knight Capital Group, Inc. [Member] Series A-1 Cumulative Perpetual Convertible Preferred Stock [Member]	Aug. 06, 2012 Knight Capital Group, Inc. [Member] Series A-2 Non-voting Cumulative Perpetual Convertible Preferred Stock [Member]
Guarantee Obligations [Line Items]
Equity commitment	$ 500,000,000								$ 291,000,000
Total committed equity capitalization of JIFN	1,000,000,000												1,200,000,000
Funded portion of equity commitment to subsidiary	107,500,000
Aggregate commitment	500,000,000								600,000,000			306,000,000	600,000,000
Unfunded portion of equity commitment to subsidiary	392,500,000
Increase in equity commitment to JFIN													100,000,000
Line of credit facility commitment under joint venture				1,000,000,000
Extension period	1
Termination notice period	60
Funded portion line of credit commitment	221,700,000
Loan commitment	500,000,000
Interest income					4,100,000
Unfunded commitment fees					300,000
Maturity date description	Scheduled to mature on March 1, 2014 with automatic one year extensions subject to a 60 day termination notice by either party
Committed line of credit facility amount														700,000,000
Net earnings from equity method investment						36,600,000	30,100,000		7,300,000	13,600,000						6,500,000	(347,100,000)
Fees earned to JFIN related to originations of loans by JFIN	31,000,000	23,700,000
Fees paid to JFIN related to origination of loans by JFIN	800,000	3,800,000
Administrative services						15,700,000	10,900,000		600,000	200,000
Administrative services						17,200,000		32,100,000	62,000		37,000
Funded portion of equity commitment to subsidiary									193,400,000		110,000,000
Percentage of the Variable Interest Entity's (VIE) voting interest									48.50%
Aggregate fair market value of derivative transactions outstanding									3,300,000
Recognized gains within Principal transaction revenues									200,000
Purchased preferred stock in exchange for cash consideration																		125,000,000
Preferred stock issued under Purchase Agreement																			24,876	100,124
Conversion of preferred stock to common stock, conversion rate																		666.667
Percentage of outstanding common stock owned															23.00%
Recognized changes in the fair value of equity method investment of															26,500,000
Securities borrowed	5,315,488,000		5,094,679,000												5,900,000
Securities loaned	$ 1,902,687,000		$ 1,934,355,000												$ 26,900,000