Leases - Summary of Future Minimum Lease Payments under Operating Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Operating Leases, After Adoption
Remainder of 2019 (three months)	$ 108
2020	433
Total future minimum lease payments	541
Less: imputed interest	(19)
Total operating lease liabilities	$ 522	$ 11,900
Operating Leases, Before Adoption
2019		726
2020		333
Total		$ 1,059