Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2017			$ 2,176
Other comprehensive income and pension reclassification	$ (2,291)	$ 518	(1,240)	$ 2,461
Balance at June 30, 2018	936		936
Foreign currency
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2017			2,756
Other comprehensive income and pension reclassification			(1,300)
Balance at June 30, 2018	1,456		1,456
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			60
Balance at June 30, 2018	$ (520)		$ (520)