Investments - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2010
Schedule of Investments [Line Items]
Income from Equity Method Investments	$ 2,562,000	$ 2,298,000	$ 7,226,000	$ 6,842,000
Net Realized and Unrealized Gains (Losses) on Private Equity Fund Investments, Including Performance Fees	(49,000)	(337,000)	(176,000)	(195,000)
Previously Received Carried Interest Subject to Repayment	0		0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	4,754,000		4,754,000		$ 5,445,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	7,318,000		7,318,000		8,048,000
Unfunded Commitments for Capital Contributions	12,045,000		12,045,000
Equity Method Investments [Member]
Schedule of Investments [Line Items]
Amortization of Intangible Assets	171,000	223,000	513,000	669,000
2015 Private Company Securities [Member]
Schedule of Investments [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	1,079,000		1,079,000		1,079,000
2019 Private Company Securities [Member]
Schedule of Investments [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	$ 642,000		$ 642,000
ABS [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage	46.00%		46.00%
Income from Equity Method Investments	$ 1,936,000	1,997,000	$ 5,588,000	5,760,000
Atalanta Sosnoff [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage	49.00%		49.00%
Income from Equity Method Investments	$ 344,000	$ 301,000	$ 882,000	785,000
Luminis [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage	20.00%		20.00%
Income from Equity Method Investments	$ 282,000		$ 756,000	$ 297,000
G5 [Member]
Schedule of Investments [Line Items]
Debt Securities, Held-to-maturity	8,851,000		8,851,000		9,717,000
Trilantic VI [Member]
Schedule of Investments [Line Items]
Other Ownership Interests, Contributed Capital	3,015,000		3,015,000
Investment	3,015,000		3,015,000
Capital Commitment	12,000,000		12,000,000
Unfunded Commitments for Capital Contributions	8,985,000		8,985,000
Trilantic IV [Member]
Schedule of Investments [Line Items]
Investment					1,178,000
Trilantic V [Member]
Schedule of Investments [Line Items]
Investment	146,000		146,000		4,980,000
Capital Commitment	5,000,000		5,000,000
Unfunded Commitments for Capital Contributions	436,000		436,000
Trilantic [Member]
Schedule of Investments [Line Items]
Issued LP Units (in shares)						500,000
Limited Partnership Investment						$ 16,090,000
Investment	6,771,000		6,771,000		9,932,000
Glisco [Member]
Schedule of Investments [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	$ 899,000		$ 899,000		$ 1,609,000