Commitments, Contingencies and Guarantees (Details) (USD $) In Millions	9 Months Ended													9 Months Ended						9 Months Ended
	Aug. 31, 2011	Aug. 26, 2011	Feb. 25, 2011	Nov. 30, 2010	Nov. 30, 2010 Jefferies Finance L P [Member]	Aug. 31, 2011 Jefferies Capital Partners IV L.P. [Member]	Aug. 31, 2011 Jefferies Capital Partners V L.P. [Member]	Aug. 31, 2011 Other Investments [Member]	Aug. 31, 2011 Jefferies Loan Core LLC [Member]	Aug. 31, 2011 Revolving credit facility [Member]	Feb. 28, 2011 Revolving credit facility [Member]	Aug. 31, 2011 Jefferies Employee Partners IV, LLC [Member]	Aug. 31, 2011 A - rated securities [Member]	Aug. 31, 2011 AAA - rated securities [Member]	Aug. 31, 2011 AAA - rated securities [Member] Index Credit Default Swaps [Member]	Aug. 31, 2011 AA/Aa [Member]	Aug. 31, 2011 AA/Aa [Member] Index Credit Default Swaps [Member]	Aug. 31, 2011 BBB/Baa [Member]	Aug. 31, 2011 Non - investment grade [Member]	Aug. 31, 2011 External Credit Rating, Non Investment Grade [Member]	Aug. 31, 2011 External Credit Rating, Non Investment Grade [Member] Credit Default Swap [Member]	Aug. 31, 2011 External Credit Rating, Non Investment Grade [Member] Index Credit Default Swaps [Member]	Aug. 31, 2011 Unrated [Member]	Aug. 31, 2011 Equity Commitments [Member]	Aug. 31, 2011 Loan Commitments [Member]	Aug. 31, 2011 Mortgage-related commitments [Member]	Aug. 31, 2011 Forward starting repos [Member]	Aug. 31, 2011 Derivative Contracts Non Credit Related [Member]	Aug. 31, 2011 Derivative Contracts - Credit Related [Member]	Aug. 31, 2011 Derivatives [Member]	Aug. 31, 2011 Credit Default Swap [Member]	Aug. 31, 2011 Index Credit Default Swaps [Member]
Line of Credit Facility [Line Items]
Equity Commitments	$ 1,000.0				$ 500.0	$ 5.7	$ 64.7	$ 6.0	$ 600.0
Funded equity commitments	117.5								117.5
Unfunded equity commitments	392.5								173.5
Loan Commitments				150.0							500.0	54.0
Funded loan Commitments										194.7		43.6
Unfunded Loan Commitments										305.3		10.4
Commitments and guarantees
2011	14,268.1																							0.5	33.2	542.4	0.2	13,681.8	10.0	13,691.8
2012	12,535.2																							0.2	12.1	23.6		12,499.3		12,499.3
2013 and 2014	52,147.1																							7.6	381.0	815.9		50,550.6	392.0	50,942.6
2015 and 2016	656.7																							2.9	67.6				586.2	586.2
2017 and Later	704.1																							631.1	33.0				40.0	40.0
Notional/ Maximum Payout	80,311.2																							642.3	526.9	1,381.9	0.2	76,731.7	1,028.2	77,759.9
Commitments and Guarantee Obligations External Credit Rating
Loan commitments	526.9															30.0		73.0		54.1			369.8
Derivative contracts- credit related:
External credit ratings for derivative contract credit	0													0	20.0	0	345.0			0	0	412.0	251.2								0	1,028.2
Total credit related commitments	1,555.1													20.0		375.0		73.0		466.1			621.0
Corporate Lending Commitments and Funded Loans
0 - 12 Months	116.1												10.0					32.7	42.1				31.3
1-5 Years	717.5																	43.3	38.7				635.5
Greater Than 5 Years	28.0												20.0					8.0
Total Corporate Lending Exposure	861.6												30.0					84.0	80.8				666.8
Corporate Lending Exposure at Fair Value	334.7																	11.0	26.7				297.0
Corporate Lending Commitments	526.9												30.0					73.0	54.1				369.8
Commitments Contingencies and Guarantees (Textuals) [Abstract]
Corporate lending exposure carried at fair value included in financial instruments owned	337.1
Corporate lending exposure carried at fair value included in financial instruments sold	(2.4)
Loan commitments outstanding to clients	211.2
Fair value of loan commitments	(2.4)			0.1
Secured revolving credit facility	950.0	950.0	1,000.0
Total committed equity capitalization incremental to each partner			250.0
Maximum payout value of derivative contracts deemed to meet the definition of a guarantee	(312.9)
Fair value of mortgage-related commitments																										4.0
Maximum payout value of derivative contracts deemed to meet the definition of a guarantee	$ 80,311.2																							$ 642.3	$ 526.9	$ 1,381.9	$ 0.2	$ 76,731.7	$ 1,028.2	$ 77,759.9