Restructuring (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring expense	$ 1,906	$ 2,076	$ 2,084	$ 2,315
Restructuring liability	$ 2,577		$ 2,577		$ 2,338	$ 2,551