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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 158,426	$ 95,926	$ 154,638	$ 93,752
Total other comprehensive income (loss)	758	(123)	1,535	(1,957)
Ending balance	162,410	181,261	162,410	181,261
Foreign Currency [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(16,251)
Other comprehensive income (loss) before reclassifications			1,535
Total other comprehensive income (loss)			1,535
Ending balance	(14,716)		(14,716)
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(2,029)
Other comprehensive income (loss) before reclassifications			0
Total other comprehensive income (loss)			0
Ending balance	(2,029)		(2,029)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(17,503)	(16,375)	(18,280)	(14,541)
Other comprehensive income (loss) before reclassifications			1,535
Total other comprehensive income (loss)			1,535
Ending balance	$ (16,745)	$ (16,498)	$ (16,745)	$ (16,498)