Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Investments in securities [Abstract]
Total investments in securities	$ 36,419	$ 32,975	$ 37,954
Securities sold, not yet purchased [Abstract]
Total securities sold, not yet purchased	0	129	0
Recurring Basis [Member]
Assets
Cash equivalents	27,909	13,538	11,107
Investments in securities [Abstract]
AFS - Common stocks	36,402	32,607	37,954
Trading - Common stocks	17	368	0
Total investments in securities	36,419	32,975	37,954
Total assets at fair value	64,328	46,513	49,061
Securities sold, not yet purchased [Abstract]
Trading - Common Stocks	0	129	0
Total securities sold, not yet purchased	0	129	0
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets
Cash equivalents	27,909	13,538	11,107
Investments in securities [Abstract]
AFS - Common stocks	36,402	32,607	37,954
Trading - Common stocks	17	368	0
Total investments in securities	36,419	32,975	37,954
Total assets at fair value	64,328	46,513	49,061
Securities sold, not yet purchased [Abstract]
Trading - Common Stocks	0	129	0
Total securities sold, not yet purchased	0	129	0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets
Cash equivalents	0	0	0
Investments in securities [Abstract]
AFS - Common stocks	0	0	0
Trading - Common stocks	0	0	0
Total investments in securities	0	0	0
Total assets at fair value	0	0	0
Securities sold, not yet purchased [Abstract]
Trading - Common Stocks	0	0	0
Total securities sold, not yet purchased	0	0	0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets
Cash equivalents	0	0	0
Investments in securities [Abstract]
AFS - Common stocks	0	0	0
Trading - Common stocks	0	0	0
Total investments in securities	0	0	0
Total assets at fair value	0	0	0
Securities sold, not yet purchased [Abstract]
Trading - Common Stocks	0	0	0
Total securities sold, not yet purchased	$ 0	$ 0	$ 0