Summary of Significant Accounting Policies - The Balances in the Company's Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 93,752
Reclassification of stranded tax effects to retained earnings	315
Total other comprehensive income (loss)	(1,834)	$ 901
Ending balance	95,926
Foreign Currency [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(12,750)
Other comprehensive income (loss) before reclassifications	(1,720)
Reclassification of stranded tax effects to retained earnings	0
Total other comprehensive income (loss)	(1,720)
Ending balance	(14,470)
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(1,791)
Other comprehensive income (loss) before reclassifications	201
Reclassification of stranded tax effects to retained earnings	(315)
Total other comprehensive income (loss)	(114)
Ending balance	(1,905)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(14,541)
Other comprehensive income (loss) before reclassifications	(1,519)
Reclassification of stranded tax effects to retained earnings	(315)
Total other comprehensive income (loss)	(1,834)
Ending balance	$ (16,375)