Investments of Operating Entities and Consolidated Funds - Equity Method Investments (Details) (USD $)							3 Months Ended		6 Months Ended					3 Months Ended		6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Clawback Obligation [Member]		Jun. 30, 2012 Operating Entities [Member] entities	Dec. 31, 2011 Operating Entities [Member]	Jun. 30, 2012 Operating Entities [Member] Net Gains (Losses) on Securities, Derivatives and Other Investments [Member]	Jun. 30, 2011 Operating Entities [Member] Net Gains (Losses) on Securities, Derivatives and Other Investments [Member]	Jun. 30, 2012 Operating Entities [Member] Net Gains (Losses) on Securities, Derivatives and Other Investments [Member]	Jun. 30, 2011 Operating Entities [Member] Net Gains (Losses) on Securities, Derivatives and Other Investments [Member]	Jun. 30, 2012 Operating Entities [Member] CBOE Stock Exchange, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] RCG Longview Partners II, LLC [Member] Clawback Obligation [Member] Accounts Payable, Accrued Expenses and Other Liabilities [Member]		Jun. 30, 2012 Operating Entities [Member] Equity Method Investee, Exceeded Threshold for Income Test [Member]	Jun. 30, 2011 Operating Entities [Member] Equity Method Investee, Exceeded Threshold for Income Test [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investee, Exceeded Threshold for Income Test [Member]	Jun. 30, 2011 Operating Entities [Member] Equity Method Investee, Exceeded Threshold for Income Test [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] RCG Longview Debt Fund IV Management, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] RCG Longview Debt Fund IV Management, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] Healthcare Royalty GP, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] Healthcare Royalty GP, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] Healthcare Royalty GP II, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] Healthcare Royalty GP II, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] CBOE Stock Exchange, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] CBOE Stock Exchange, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] Starboard Value L.P. [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] Starboard Value L.P. [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] RCG Longview Partners, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] RCG Longview Partners, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] RCG Longview Louisiana Manager, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] RCG Longview Louisiana Manager, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] RCG Urban American, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] RCG Urban American, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] RCG Urban American Management, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] RCG Urban American Management, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] RCG Longview Equity Management, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] RCG Longview Equity Management, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] Urban American Real Estate Fund II, L.P. [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] Urban American Real Estate Fund II, L.P. [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] RCG Kennedy House, LLC [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] RCG Kennedy House, LLC [Member]	Jun. 30, 2012 Operating Entities [Member] Equity Method Investments [Member] Equity Method Investee, Other [Member]	Dec. 31, 2011 Operating Entities [Member] Equity Method Investments [Member] Equity Method Investee, Other [Member]	Jun. 30, 2012 Operating Entities [Member] Minimum [Member]	Jun. 30, 2012 Operating Entities [Member] Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage											9.70%																																			30.00%	55.00%
Number of entities in which Company holds a majority					3
Other investments	$ 68,336,000	$ 59,943,000			$ 68,336,000	$ 59,943,000												$ 19,443,000	$ 16,687,000	$ 1,254,000	$ 1,980,000	$ 629,000	$ 513,000	$ 412,000	$ 258,000	$ 2,176,000	$ 2,423,000	$ 7,328,000	$ 3,693,000	$ 1,832,000	$ 1,569,000	$ 1,567,000	$ 1,140,000	$ 1,319,000	$ 1,258,000	$ 532,000	$ 1,096,000	$ 196,000	$ 557,000	$ 1,488,000	$ 1,541,000	$ 383,000	$ 323,000	$ 327,000	$ 336,000
Contractual obligation			6,200,000	[1]								6,200,000	[1]
Income (loss) from equity method investments							3,600,000	1,200,000	7,800,000	2,400,000
Equity Method Investment, Summarized Financial Information [Abstract]
Revenues														6,383,000	600,000	9,651,000	600,000
Expenses														(2,419,000)	(471,000)	(2,747,000)	(471,000)
Net realized and unrealized gains (losses)														20,000	(4,000)	57,000	(4,000)
Net Income														$ 3,984,000	$ 125,000	$ 6,961,000	$ 125,000

[1] Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 14 for further information on capital lease minimum payments.