Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating losses	$ 14,848	$ 9,180
R&D credits	12,506	1,776
Deferred revenue	8,159
Deferred rent	2,854	113
Capitalized R&D costs	1,375	1,362
Equity compensation	443	27
Accrued expense and other	115	196
Total deferred tax assets	40,300	12,654
Deferred tax liabilities:
Depreciation	(2,680)	(166)
Total deferred tax liabilities	(2,680)	(166)
Valuation allowance	$ (37,620)	$ (12,488)