Other liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Other current liabilities
Lease liability	$ 3,306		$ 3,193
Total other current liabilities	3,306	$ 3,193	3,193
Other non-current liabilities
Lease liability	30,088		30,975
Other	1,001		1,001
Total other non-current liabilities	$ 31,089	$ 31,976	$ 31,976