Income Taxes - Schedule of Significant Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets (liabilities)
Deferred revenue	$ 0	$ 40,961
License and technology payments	7,221	8,222
Share-based compensation	20,342	17,599
Accrued expenses	371	608
Depreciation, deferred tax liability	(28)
Depreciation, deferred tax assets		81
Federal and state net operating loss carryforwards	88,766	76,309
Research and development credits	5,933	3,782
Other	5	3,534
Deferred income tax assets	122,610	151,096
Valuation allowance	(122,610)	(147,567)
Net deferred tax assets	$ 0	$ 3,529