Quarterly Results (unaudited) (Tables)

12 Months Ended

Dec. 31, 2015

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Results

	Three Months Ended
	March 31,			June 30,			September 30,			December 31,
	2015			2015			2015			2015
	(in thousands, except per share data)
	(unaudited)
Operating expenses	$	10,896		$	10,889		$	19,678		$	20,050
Loss from operations	$	(10,896	)	$	(10,889	)	$	(19,678	)	$	(20,050	)
Other income (expense), net	$	201		$	200		$	203		$	193
Net loss	$	(10,695	)	$	(10,689	)	$	(19,475	)	$	(19,857	)
Net loss per share applicable to common    stockholders—basic and diluted	$	(0.53	)	$	(0.40	)	$	(0.68	)	$	(0.66	)
	Three Months Ended
	March 31,			June 30,			September 30,			December 31,
	2014			2014			2014			2014
	(in thousands, except per share data)
	(unaudited)
Operating expenses	$	9,909		$	7,840		$	9,584		$	10,607
Loss from operations	$	(9,909	)	$	(7,840	)	$	(9,584	)	$	(10,607	)
Other income (expense), net	$	212		$	222		$	236		$	237
Net loss	$	(9,697	)	$	(7,618	)	$	(9,348	)	$	(10,370	)
Net loss per share applicable to common    stockholders—basic and diluted	$	(43.37	)	$	(0.39	)	$	(0.47	)	$	(0.52	)