Leases - Maturities of lease liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Operating Leases
2020	$ 5,461
2021	5,358
2022	5,316
2023	5,294
2024	5,302
more than 5 years	11,270
Total	38,001
Less: Interest	(10,298)
Present value of lease liabilities	27,703
Finance Leases
2020	41
2021	41
2022	41
2023	41
2024	0
more than 5 years	0
Total	164
Less: Interest	(13)
Present value of lease liabilities	151
2020	5,502
2021	5,399
2022	5,357
2023	5,335
2024	5,302
more than 5 years	11,270
Total	38,165
Less: Interest	(10,311)
Present value of lease liabilities	$ 27,854	$ 27,800