Restructuring (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring expense	$ 722	$ 0	$ 2,806	$ 2,315
Restructuring liability	$ 1,249		$ 1,249		$ 2,338	$ 2,551