Accounts payable, accrued liabilities and long-term liabilities - Summary (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accounts payable	$ 10,067	$ 8,531
Accrued clinical expense	10,506	10,154
Accrued development and other expense	1,454	1,243
Accrued compensation and benefits	2,438	5,847
Total accounts payable and accrued liabilities	24,465	25,775
Long-term liabilities	$ 704	732
Deferred revenue		100
Other liabilities		$ 600