Income Taxes - Schedule of Deferred Income Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Net operating losses and tax credits	$ 22,003	$ 26,296
Property and equipment	5,969	8,289
AMT minimum tax receivable	1,348	2,489
Accruals and accrued loss contingencies	5,776	4,833
Capitalized research and development costs	14,220	9,108
Gross deferred income tax assets	49,316	51,015
Intangible assets	(2,711)	(3,075)
Prepaid and other expenses	(121)	(261)
Gross deferred income tax liabilities	(2,832)	(3,336)
Net deferred income tax assets	$ 46,484	$ 47,679