Leases - Lease right-of-use assets and liabilities (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Lease Right-of-Use Assets
Operating lease right-of-use assets	$ 8,343
Finance lease right-of-use assets	$ 318
Finance Lease, Right-of-Use Asset, balance sheet location	us-gaap:PropertyPlantAndEquipmentNet
Lease right-of-use assets	$ 8,661
Operating lease liabilities	8,864
Finance lease liabilities	$ 640
Finance lease liabilities, balance sheet location	us-gaap:LongTermDebt
Lease liabilities	$ 9,504