Summary of Significant Accounting Policies - The Balances in the Company's Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 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)	$ (123)	$ 210	(1,957)	$ 1,111
Ending balance	181,261		181,261
Foreign Currency [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(12,750)
Other comprehensive income (loss) before reclassifications			(1,843)
Reclassification of stranded tax effects to retained earnings			0
Total other comprehensive income (loss)			(1,843)
Ending balance	(14,593)		(14,593)
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)		(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			(1,642)
Reclassification of stranded tax effects to retained earnings			(315)
Total other comprehensive income (loss)			(1,957)
Ending balance	$ (16,498)		$ (16,498)