Stock-based compensation (Tables)

3 Months Ended

Mar. 31, 2016

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,
	2016		2015
Research and development expense	$	1,458	$	808
General and administrative expense	1,580		1,508
	$	3,038	$	2,316