Summary of Significant Accounting Policies - Revised Total Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in Stockholders' Equity
Balance				$ 253,161				$ 245,156	$ 253,161	$ 245,156	$ 203,533
Net income (loss)	$ (25,837)	$ 2,755	$ 110	573	$ 5,012	$ 478	$ 2,825	2,199	(22,399)	10,514	42,151
Foreign currency translation adjustment									4,029	(2,488)	(3,292)
Restricted stock awards									3,466	2,766	3,835
Tax payments for stock issuances									(640)	(1,051)	(837)
Tax benefits of stock based compensation											318
Pension adjustment, net of tax of $509 in 2016 and $70 in 2015									313	(1,736)	(552)
Balance	$ 237,930				253,161				237,930	253,161	245,156
Pension adjustment, tax amount									53	509	70
As Previously Reported
Change in Stockholders' Equity
Balance				256,578				248,048	256,578	248,048	205,873
Net income (loss)										10,514	42,151
Foreign currency translation adjustment										(2,488)	(3,292)
Restricted stock awards										2,766	3,835
Tax payments for stock issuances										(1,051)	(837)
Tax benefits of stock based compensation											318
Pension adjustment, net of tax of $509 in 2016 and $70 in 2015										(1,211)
Balance					256,578					256,578	248,048
Adjustment
Change in Stockholders' Equity
Balance				$ (3,417)				$ (2,892)	$ (3,417)	(2,892)	(2,340)
Pension adjustment, net of tax of $509 in 2016 and $70 in 2015										(525)	(552)
Balance					$ (3,417)					$ (3,417)	$ (2,892)