Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2017	$ 2,176
Other comprehensive income and pension reclassification	1,051	$ 1,943
Balance at March 31, 2018	3,227
Foreign currency
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2017	2,756
Other comprehensive income and pension reclassification	1,021
Balance at March 31, 2018	3,777
Defined benefit pension plan
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2017	(580)
Other comprehensive income and pension reclassification	30
Balance at March 31, 2018	$ (550)