Summary of Significant Accounting Policies - Revised Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in Stockholders' Equity
Balance	$ (12,910)	$ (8,686)	$ (4,842)
Foreign currency translation adjustment	4,029	(2,488)	(3,292)
Pension adjustment, net of tax of $509 in 2016 and $70 in 2015	313	(1,736)	(552)
Balance	(8,568)	(12,910)	(8,686)
Pension adjustment, tax amount	53	509	70
As Previously Reported
Change in Stockholders' Equity
Balance	(9,493)	(5,794)	(2,502)
Foreign currency translation adjustment		(2,488)	(3,292)
Pension adjustment, net of tax of $509 in 2016 and $70 in 2015		(1,211)
Balance		(9,493)	(5,794)
Adjustment
Change in Stockholders' Equity
Balance	$ (3,417)	(2,892)	(2,340)
Pension adjustment, net of tax of $509 in 2016 and $70 in 2015		(525)	(552)
Balance		$ (3,417)	$ (2,892)