Acquisition of the Global Commodities Group (Details Textuals) (USD $)	3 Months Ended		8 Months Ended	9 Months Ended
	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2010	Aug. 31, 2011	Aug. 26, 2011	Jul. 01, 2011	Feb. 25, 2011
Acquisition of Bache Global Commodities Group (Textuals) [Abstract]
Total cash payment for acquisition						$ 422,013,000
Percentage of equity interests acquired						100.00%
Fair values of net assets acquired, including identifiable intangible assets	474,500,000			474,500,000		474,522,000
Purchase price of net assets acquired	422,000,000			422,000,000		422,013,000
Bargain purchase gain	52,509,000			52,509,000
Fair value of intangible assets	18,300,000			18,300,000
Fair value of exchange and clearing organization membership interests and registrations	11,200,000			11,200,000
Fair value of internally developed software	6,300,000			6,300,000
Revenue contributed by the global commodities group	43,500,000
Net income contributed by the global commodities group	6,400,000
Bargain purchase gain excluded from the revenues and net income				52,500,000
Acquisition costs recognized in Professional services	4,400,000			4,400,000
Additional amortization on the intangibles assets and internally developed software	200,000	70,000	1,900,000	1,600,000
Effective tax rate from the proforma condensed combined financial results	44.90%	45.40%	33.80%	36.50%
Revolving credit facility	950,000,000			950,000,000	950,000,000		1,000,000,000
Cash payment for business acquisition						419,500,000
Additional payment anticipated for business acquisition						2,500,000
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value of trade name (or intangible asset)	5,800,000			5,800,000
Weighted Average Useful life of intangible assets				9.6
Trade names (intangible assets) [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Fair value of trade name (or intangible asset)	$ 1,300,000			$ 1,300,000
Weighted Average Useful life of intangible assets				1.5