Fixed Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fixed Assets [Abstract]
Depreciation and amortization of fixed assets		$ 1,822	$ 2,280	$ 2,312
Unamortized computer software costs		200	800
Amortization of computer software costs		$ 600	$ 700	$ 700
Fully depreciated assets disposed of	$ 2,100