Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax assets:
Allowance for uncollectible accounts receivable	$ 606	$ 467
Accrued compensation expense	7,414	5,154
Inventory differences	1,269	2,505
Net operating loss carryforwards	20,226	15,741
Deferred revenue	46	58
Stock-based compensation expense	2,833	2,281
Other	9,243	8,986
Total deferred income tax assets	41,637	35,192
Deferred income tax liabilities:
Prepaid expenses	(1,142)	(930)
Property and equipment	(20,045)	(20,352)
Intangible assets	(58,883)	(28,588)
Foreign withholding tax	(5,590)	0
Other	(4,350)	(1,830)
Total deferred income tax liabilities	(90,010)	(51,700)
Valuation allowance	(4,989)	(4,422)
Net deferred income tax liabilities	(53,362)	(20,930)
Reported as:
Deferred income tax assets - Long-term	3,001	2,359
Deferred income tax liabilities - Long-term	(56,363)	(23,289)
Net deferred income tax liabilities	$ (53,362)	$ (20,930)