Stock-based compensation (Tables)

6 Months Ended

Jun. 30, 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 June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
Research and development expense	$	1,478	$	931	$	2,936	$	1,739
General and administrative expense	810		1,861		2,390		3,369
	$	2,288	$	2,792	$	5,326	$	5,108