Lease liabilities - Supplemental Cash flow Information Related to Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Capital Leases, Net Investment in Direct Financing and Sales Type Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 236
Cash paid for amounts included in the measurement of finance lease liabilities	9
Operating lease liabilities arising from obtaining right-of-use assets	$ 1,182