Leases - Supplemental cash flow information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 2,394	$ 2,271
Operating cash flows from finance leases	21	20
Financing cash flows from finance leases	$ 116	$ 87	$ 0