Income Taxes - Components of Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 27,726	$ 16,490
Tax credit carryforwards	5,259	2,014
Accrued expenses	2,079	7,353
Capitalized patent costs	26,307	16,025
Deferred revenue	7,151	9,672
Construction financing lease obligation	9,352	13,685
Other	4,978	2,979
Total deferred tax assets	82,852	68,218
Less valuation allowance	(73,301)	(54,300)
Net deferred tax assets	9,551	13,918
Deferred tax liabilities - depreciation and amortization	$ (9,551)	$ (13,918)