Stock-based compensation (Tables)

9 Months Ended

Sep. 30, 2015

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 September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Research and development expense	$	959	$	859	$	2,698	$	1,929
General and administrative expense	1,845		1,732		5,214		2,893
	$	2,804	$	2,591	$	7,912	$	4,822