Accounts payable and accrued liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Payables and Accruals [Abstract]
Accounts payable	$ 2,729		$ 6,296
Accrued expenses	6,080		5,743
Accrued compensation and benefits	2,644		2,923
Current portion of deferred rent	2,127		40
Total accounts payable and accrued liabilities	13,580		$ 15,002
Cash proceeds generated from exercise of warrants	$ 2,100	$ 2,100