Long-Term Investments (Equity-Method Investments) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 12,566		$ 11,631
Proceeds from long-term equity method investment	$ 427	$ 414
Percent of other investments redeemed that qualify for the NAV practical expedient	25.00%
In-transit redemptions recorded from proceeds from investments redeemed that qualify for NAV practical expedient	$ 3,984
Equity in losses from investments	(1,362)	$ (1,162)
Indian Creek Investors LP (“Indian Creek”)
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 1,353		1,167
Equity-method ownership percentage	12.58%
Boyar Value Fund (“Boyar”)
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 9,041		8,384
Equity-method ownership percentage	34.38%
Quoted market value	$ 9,041
Ladenburg Thalmann Financial Services Inc. (“LTS”)
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 2,172		2,080
Equity-method ownership percentage	10.20%
Quoted market value	$ 42,991
Castle Brands, Inc. (“Castle”)
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 0		$ 0
Equity-method ownership percentage	7.64%
Quoted market value	$ 9,027