Balance Sheet Accounts and Supplemental Disclosures - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued compensation	$ 6,365	$ 4,102
Operating lease liabilities	2,291
Accrued professional service fees	2,059	2,697
Accrued other	728	769
Total accrued expenses	$ 11,443	$ 7,568