Restructuring Activities (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) Position	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Restructuring Activities [Abstract]
Restructuring and related cost, expected number of positions eliminated | Position	40
Expected restructuring costs	$ 2,200
Restructuring cost, cost incurred to date	2,000
Restructuring charges	0	$ 917	$ 1,300
Cumulative translation adjustment	1,700
Tax benefit	1,000
Payments	$ (52)