Leases - Consolidated balance sheet information (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance sheet information related to leases
Operating lease assets	$ 2,920	$ 3,044
Operating lease right-of-use assets (Classification)	Us-gaap:OperatingLeaseRightOfUseAsset	Us-gaap:OperatingLeaseRightOfUseAsset
Finance lease assets	$ 2,181	$ 2,580
Finance Lease, Assets (Balance Sheet Location)	us-gaap:PropertyPlantAndEquipmentNet	us-gaap:PropertyPlantAndEquipmentNet
Total leased assets	$ 5,101	$ 5,624
Operating Lease, Current Liabilities	$ 707	$ 681
Operating Lease, Current Liabilities (Balance Sheet Location)	Us-gaap:OperatingLeaseLiabilityCurrent	Us-gaap:OperatingLeaseLiabilityCurrent
Finance Lease, Current Liabilities	$ 534	$ 836
Finance Lease, Current Liabilities (Balance Sheet Location)	us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent	us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent
Operating Lease, Non-current Liabilities	$ 3,067	$ 3,254
Operating Lease, Non-current Liabilities (Balance Sheet Location)	Us-gaap:OperatingLeaseLiabilityNoncurrent	Us-gaap:OperatingLeaseLiabilityNoncurrent
Finance Lease, Non-current Liabilities	$ 307	$ 331
Finance Lease, Non-current Liabilities (Balance Sheet Location)	us-gaap:LongTermDebtAndCapitalLeaseObligations	us-gaap:LongTermDebtAndCapitalLeaseObligations
Total lease liabilities	$ 4,615	$ 5,102