Restructuring and Exit Costs (Summary of Restructuring Liability by Plan) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Costs incurred	$ (26)	$ 2,232
February 2017 Plan
Restructuring Reserve [Roll Forward]
Restructuring liability	0	0
Costs incurred	0	997
Restructuring cash payments	0	(855)
Accruals released	0	(142)
Restructuring liability	0	0
September 2017 Plan
Restructuring Reserve [Roll Forward]
Restructuring liability	817	0
Costs incurred	45	1,275
Restructuring cash payments	(705)	(431)
Accruals released	(157)	(27)
Restructuring liability	$ 0	$ 817