Investment in Securities, Investment in Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Trading securities [Abstract]
Cost	$ 17,578	$ 37	$ 20
Fair value	31,407	45	24
Available for sale securities [Abstract]
Cost	0	17,540	18,838
Fair value	0	36,745	33,166
Total investments in securities [Abstract]
Cost	17,578	17,577	18,858
Fair value	31,407	36,790	33,190
Common Stock [Member]
Trading securities [Abstract]
Cost	17,467	26	20
Fair value	31,291	34	24
Available for sale securities [Abstract]
Cost	0	17,441	18,739
Fair value	0	36,637	33,058
Mutual Funds [Member]
Trading securities [Abstract]
Cost	12	11	0
Fair value	11	11	0
Closed End Funds [Member]
Trading securities [Abstract]
Cost	99	0	0
Fair value	105	0	0
Available for sale securities [Abstract]
Cost	0	99	99
Fair value	$ 0	$ 108	$ 108