Restructuring and Exit Costs (Schedule of Restructuring and Exit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Costs incurred	$ 0	$ (57)
September 2017 Restructuring Plan | Employee Severance Costs
Restructuring Reserve [Roll Forward]
Restructuring liability as of December 31, 2017	$ 817		$ 0
Costs incurred		45	1,275
Amounts paid		(423)	(431)
Accruals released		(102)	$ (27)
Restructuring liability as of March 31, 2018		$ 337