Long-Term Investments (Equity-Method Investments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 11,631	$ 11,631	$ 15,841
Proceeds from long-term equity method investment	(13,952)	$ (7,007)	(1,239)	$ (1,158)
Percent of other investments redeemed that qualify for the NAV practical expedient		50.00%
Equity in (earnings) losses from long-term investments		$ (3,158)	765	$ 2,754
Indian Creek Investors LP (“Indian Creek”)
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 1,167	$ 1,167	4,498
Equity method ownership percentage	12.61%	12.61%
Percent of other investments redeemed that qualify for the NAV practical expedient		50.00%
Boyar Value Fund (“Boyar”)
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 8,384	$ 8,384	9,026
Equity method ownership percentage	34.27%	34.27%
Quoted market value	$ 8,384	$ 8,384
Ladenburg Thalmann Financial Services Inc. (“LTS”)
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 2,080	$ 2,080	2,317
Equity method ownership percentage	10.36%	10.36%
Quoted market value	$ 35,396	$ 35,396
Castle Brands
Schedule of Equity Method Investments [Line Items]
Equity-method investments	$ 0	$ 0	$ 0
Equity method ownership percentage	7.66%	7.66%
Quoted market value	$ 10,961	$ 10,961
Difference between carrying value and underlying equity	695	695
Ladenburg Thalmann Financial Services
Schedule of Equity Method Investments [Line Items]
Difference between carrying value and underlying equity	$ 27,167	27,167
Maximum
Schedule of Equity Method Investments [Line Items]
Proceeds from long-term equity method investment		(5,535)
Minimum
Schedule of Equity Method Investments [Line Items]
Proceeds from long-term equity method investment		$ (1,472)