Leases - Supplemental balance sheet information (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Leases
Operating lease – right of use assets, net	$ 2,459
Current portion of operating lease liabilities, included in accrued liabilities	577
Operating lease liabilities, net of current portion	2,021
Total operating lease liabilities	$ 2,598
Weighted average remaining lease term for operating leases (in years)	4 years 5 months 5 days
Weighted average discount rate for operating leases	6.10%