Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Lease Liabilities, Payments Due [Abstract]
2019 (Remaining 3 months)	$ 632
2020	1,986
2021	1,957
2022	1,894
2023	1,951
Thereafter	7,111
Total lease payments	15,531
Less imputed interest	(3,005)
Total operating lease liabilities	12,526
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019 (Remaining 12 months)			$ 1,777
2020			1,788
2021			1,839
2022			1,894
2023			1,951
Thereafter			7,296
Total lease payment due			$ 16,545
Assets and Liabilities, Lessee [Abstract]
Current portion of operating lease liabilities	1,431	$ 1,058
Operating lease liabilities, net of current portion	11,095	$ 11,776
Total operating lease liabilities	$ 12,526