Accounts payable and accrued liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accounts payable	$ 4,266	$ 4,344
Accrued expenses	11,025	6,279
Accrued compensation and benefits	2,520	3,021
Total accounts payable and accrued liabilities	17,811	13,644
Deferred revenue and other liabilities	714	314
Deferred revenue	200	$ 300
Other liabilities	$ 500