Lease (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	[1]
Lease
Operating lease, remaining lease term	4 years 2 months 12 days
Operating lease, renewal term	5 years
Operating lease, existence of option to extend	true
Operating lease expense	$ 100	$ 100
Cash paid for amount included in the measurement of operating lease liabilities	$ 100
Discount rate used to measure lease liability	7.15%
Future minimum lease payments
Remainder of 2019	$ 304
2020	416
2021	428
2022	441
2023	201
Total future minimum lease payments	1,790
Imputed interest	(244)
Total	1,546
Operating lease liability, current portion	308		$ 0
Operating lease liability, net of current portion	$ 1,238		$ 0

[1] Condensed consolidated balance sheet as of December 31, 2018 has been derived from audited consolidated financial statements.