Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating losses	$ 41,589	$ 14,848
R&D credits	25,328	12,506
Deferred revenue	8,456	8,159
Deferred rent	2,966	2,854
Capitalized R&D costs	1,207	1,375
Equity compensation	883	443
Accrued expense and other	108	115
Total deferred tax assets	80,537	40,300
Deferred tax liabilities:
Depreciation	(2,744)	(2,680)
Total deferred tax liabilities	(2,744)	(2,680)
Valuation allowance	$ (77,793)	$ (37,620)