Leases - Supplemental unaudited consolidated balance sheet information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Supplemental unaudited consolidated balance sheet information
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Operating lease right-of-use assets
Operating lease right-of-use assets	$ 10,580
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Operating lease liabilities current
Operating lease liabilities current	$ 2,636
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OperatingLeaseLiabilityNoncurrent
Operating lease liabilities noncurrent	$ 11,299
Operating lease liabilities	$ 13,935
Weighted average remaining lease term	6 years 8 months 12 days
Weighted-average discount rate	5.00%
Supplemental unaudited interim consolidated cash flow information
Operating cash flows from operating leases	$ 3,731
ROU assets obtained in exchange for new operating lease liabilities	$ 4,924