Investments of Operating Entities and Consolidated Funds - Equity Method Investments (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Other investments	$ 99,483,000	$ 84,930,000
Operating Entities
Schedule of Equity Method Investments [Line Items]
Number of entities in which Company holds a majority	3
Other investments	99,483,000	84,930,000
Operating Entities | Net Gains (Losses) on Securities, Derivatives and Other Investments
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	16,100,000	15,600,000	5,400,000
Operating Entities | CBOE Stock Exchange, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	9.70%
Operating Entities | Equity Method Investee, Exceeded Threshold for Income Test
Equity Method Investment, Summarized Financial Information [Abstract]
Assets	626,866,000	498,557,000
Liabilities	226,138,000	20,170,000
Equity	400,728,000	478,387,000
Revenues	75,429,000	77,502,000	33,061,000
Expenses	(69,893,000)	(60,093,000)	(45,335,000)
Net realized and unrealized gains (losses)	77,042,000	5,575,000	9,365,000
Net Income	82,578,000	22,984,000	(2,909,000)
Operating Entities | RCG Longview Partners II, LLC [Member] | Clawback Obligation | Accounts Payable, Accrued Expenses and Other Liabilities
Schedule of Equity Method Investments [Line Items]
Contractual obligation	6,200,000
Operating Entities | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	25,966,000	26,462,000
Operating Entities | Equity Method Investments | RCG Longview Debt Fund IV Management, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	1,533,000	1,954,000
Operating Entities | Equity Method Investments | RCG Longview Debt Fund V Partners, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	1,497,000	0
Operating Entities | Equity Method Investments | Healthcare Royalty GP, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	794,000	642,000
Operating Entities | Equity Method Investments | Healthcare Royalty GP II, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	840,000	1,086,000
Operating Entities | Equity Method Investments | Healthcare Royalty GP III, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	47,000	0
Operating Entities | Equity Method Investments | CBOE Stock Exchange, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	1,351,000	2,058,000
Operating Entities | Equity Method Investments | Starboard Value LP
Schedule of Equity Method Investments [Line Items]
Other investments	14,263,000	12,757,000
Operating Entities | Equity Method Investments | RCG Longview Partners, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	1,839,000	1,535,000
Operating Entities | Equity Method Investments | RCG Longview Louisiana Manager, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	0	1,866,000
Operating Entities | Equity Method Investments | RCG Urban American, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	316,000	1,380,000
Operating Entities | Equity Method Investments | RCG Urban American Management, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	238,000	545,000
Operating Entities | Equity Method Investments | RCG Longview Equity Management, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	292,000	285,000
Operating Entities | Equity Method Investments | Urban American Real Estate Fund II, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	1,785,000	1,636,000
Operating Entities | Equity Method Investments | RCG Kennedy House, LLC
Schedule of Equity Method Investments [Line Items]
Other investments	502,000	377,000
Operating Entities | Equity Method Investments | Equity Method Investee, Other
Schedule of Equity Method Investments [Line Items]
Other investments	669,000	341,000
Operating Entities | Minimum
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	30.00%
Operating Entities | Maximum
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	55.00%
Starboard Value A LP [Member] | Operating Entities | Equity Method Investee, Exceeded Threshold for Income Test
Equity Method Investment, Summarized Financial Information [Abstract]
Cash	14,000
Performance Fee Receivable	25,214,000	20,448,000
Investments in Portfolio Funds	2,201,000	1,380,000
Liabilities	0	0
Equity	27,429,000	21,828,000
Performance Fee Revenues	23,098,000	20,448,000	4,750,000
Net realized and unrealized gains (losses)	283,000	254,000	18,000
Net Income	$ 23,381,000	$ 20,702,000	$ 4,768,000