Quarterly Financial Data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Recurring Adjustments Necessary for Fair Statement

The following information has been derived from unaudited consolidated financial statements that, in the opinion of management, include all recurring adjustments necessary for a fair statement of such information.

	Three Months Ended
	March 31,			June 30,			September 30,			December 31,
(in thousands, except per share amounts)	2017			2017			2017			2017
Revenues	$	0		$	0		$	0		$	355
Operating expenses		23,782			26,902			31,221			48,132
Net loss		(23,879	)		(28,880	)		(34,188	)		(50,534	)
Net loss per common share—basic and diluted	$	(0.75	)	$	(0.91	)	$	(1.07	)	$	(1.38	)
Weighted average common shares—basic and diluted		31,704			31,826			31,931			36,644

	Three Months Ended
	March 31,			June 30,			September 30,			December 31,
(in thousands, except per share amounts)	2016			2016			2016			2016
Operating expenses	$	16,673		$	14,120		$	17,435		$	21,552
Net loss		(16,815	)		(14,185	)		(17,782	)		(23,112	)
Net loss per common share—basic and diluted	$	(0.78	)	$	(0.63	)	$	(0.65	)	$	(0.79	)
Weighted average common shares—basic and diluted		21,570			22,666			27,524			29,347