Operating Leases - Schedule of Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Operating Leases, After Adoption of 842:
Remainder of 2019	$ 4,118
2020	5,560
2021	5,593
2022	5,708
2023	5,869
Thereafter	13,367
Total future minimum lease payments	40,215
Less: imputed interest	(8,608)
Total	$ 31,607
Operating Leases, Before Adoption of 842:
2019		$ 5,526
2020		5,560
2021		5,593
2022		5,708
2023		5,869
Thereafter		13,458
Total future minimum lease payments		41,714
2019		$ 5,526