Lease (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	[1]
Lease
Operating lease, remaining lease term	4 years		4 years
Operating lease, renewal term	5 years		5 years
Operating lease, existence of option to extend			true
Operating lease expense	$ 100	$ 100	$ 200	$ 200
Cash paid for amount included in the measurement of operating lease liabilities	$ 100		$ 200
Discount rate used to measure lease liability	7.15%		7.15%
Future minimum lease payments
Remainder of 2019	$ 204		$ 204
2020	416		416
2021	428		428
2022	441		441
2023	201		201
Total future minimum lease payments	1,690		1,690
Imputed interest	(216)		(216)
Total	1,474		1,474
Operating lease liability, current portion	317		317		$ 0
Operating lease liability, net of current portion	$ 1,157		$ 1,157		$ 0

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