Income Taxes - Temporary Difference (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss and credits carryforwards	$ 14,062	$ 6,592
Accrued expenses	25,889	26,263
Stock-based compensation	4,709	3,511
Other assets	241	356
Total gross deferred tax assets	44,901	36,722
Less: valuation allowance	(19,627)	(15,910)
Total net deferred tax assets	25,274	20,812
Deferred tax liabilities:
Intangible assets and goodwill	(5,628)	(5,197)
Property, plant, and equipment	(35,672)	(34,758)
Other liabilities	(1,144)	(1,495)
Total gross deferred tax liabilities	(42,444)	(41,450)
Net deferred tax liability	$ (17,170)	$ (20,638)