Investments - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2010
Schedule of Investments [Line Items]
Marketable Securities	$ 59,394,000		$ 59,394,000		$ 66,487,000
Net Realized and Unrealized Gains (Losses) on Private Equity Fund Investments, Including Performance Fees	(2,532,000)	$ 4,764,000	(2,193,000)	$ 6,131,000
Previously Received Carried Interest Subject to Repayment	0		0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	10,520,000		10,520,000		9,889,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	12,869,000		12,869,000
Unfunded Commitments for Capital Contributions	3,584,000		3,584,000
Cost Method Investments	1,079,000		1,079,000		1,079,000
Income (Loss) from Equity Method Investments	2,070,000	1,664,000	3,680,000	2,951,000
Investment Banking [Member]
Schedule of Investments [Line Items]
Income (Loss) from Equity Method Investments	113,000	290,000	(36,000)	18,000
Amortization of Intangible Assets	2,357,000	2,862,000	4,714,000	6,077,000
Trilantic [Member]
Schedule of Investments [Line Items]
Issued LP Units (in shares)						500,000
Limited Partnership Investment						$ 16,090,000
Participation in Successor Funds	12,000,000		12,000,000
Glisco [Member]
Schedule of Investments [Line Items]
Cost Method Investments	$ 2,317,000		$ 2,317,000		2,463,000
G5 Evercore [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage	49.00%		49.00%
Income (Loss) from Equity Method Investments	$ (25,000)	277,000	$ (51,000)	29,000
G5 Evercore [Member] | Special Charges [Member] | Investment Banking [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Other than Temporary Impairment	$ 14,400,000		$ 14,400,000
ABS [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage	45.00%		45.00%
Income (Loss) from Equity Method Investments	$ 1,712,000	1,244,000	$ 3,243,000	2,574,000
Atalanta Sosnoff [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage	49.00%		49.00%
Income (Loss) from Equity Method Investments	$ 326,000	143,000	$ 431,000	348,000
Luminis [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage	19.00%		19.00%
Income (Loss) from Equity Method Investments	$ 57,000		$ 57,000
Variable Interest Entity, Not Primary Beneficiary [Member] | Minimum [Member] | ECP II [Member]
Schedule of Investments [Line Items]
Percent Ownership of Carried Interest			8.00%
Variable Interest Entity, Not Primary Beneficiary [Member] | Maximum [Member] | ECP II [Member]
Schedule of Investments [Line Items]
Percent Ownership of Carried Interest			9.00%
Trilantic [Member]
Schedule of Investments [Line Items]
Investment	11,419,000		$ 11,419,000		11,632,000
Trilantic [Member] | Trilantic V [Member]
Schedule of Investments [Line Items]
Investment	213,000		213,000		3,280,000
Capital Commitment	5,000,000		5,000,000
Unfunded Commitments for Capital Contributions	1,175,000		1,175,000
Trilantic [Member] | Trilantic IV [Member]
Schedule of Investments [Line Items]
Investment					1,178,000
Equity Method Investments [Member]
Schedule of Investments [Line Items]
Amortization of Intangible Assets	391,000	$ 884,000	781,000	$ 1,764,000
Private Equity Funds [Member]
Schedule of Investments [Line Items]
Equity Method Investment	14,637,000		14,637,000		21,742,000
Private Equity Funds [Member] | ECP II [Member]
Schedule of Investments [Line Items]
Equity Method Investment	851,000		851,000		$ 933,000
Cash	827,000		827,000
Marketable Securities	$ 24,000		$ 24,000