Commitments and Contingencies - Schedule of Maturity of Company's Operating Lease Liabilities (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019 (remaining nine months)	$ 4,153
2020	5,659
2021	5,332
2022	5,460
2023	5,570
Thereafter	35,836
Total undiscounted lease payments	62,010
Present value adjustment	27,441
Total net lease liability	34,569
Operating lease liabilities	1,539
Operating lease liabilities	33,030
Total net lease liability	$ 34,569