Stock-based compensation (Tables)

3 Months Ended

Mar. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Employee Service Share-based Compensation Allocation

Total share-based compensation expense by operating statement classification is presented below (in thousands):

	Three Months Ended March 31,
	2017		2016
Research and development expense	$	982	$	1,458
General and administrative expense	784		1,580
	$	1,766	$	3,038