Restructuring (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2015
Restructuring and Related Activities [Abstract]
Restructuring expense	$ 178	$ 240
Restructuring liability	$ 1,485		$ 2,338	$ 2,551