Supplementary Data - Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Unaudited Financial Information

The following table represents certain unaudited financial information for each of the quarters ended December 31, 2017 and 2016:

	Three Months Ended
(in thousands, except per share data)	December 31, 2017		September 30, 2017			June 30, 2017			March 31, 2017
Revenue	$	27,074	$	24,144		$	8,752		$	11,653
Net income (loss)	$	621	$	(10,247	)	$	(25,216	)	$	(8,257	)
Net loss per share attributable to common stockholders,    basic and diluted	$	0.02	$	(0.28	)	$	(0.69	)	$	(0.23	)

	Three Months Ended
(in thousands, except per share data)	December 31, 2016			September 30, 2016			June 30, 2016			March 31, 2016
Revenue	$	6,272		$	3,454		$	3,094		$	2,223
Net loss	$	(14,033	)	$	(14,662	)	$	(14,176	)	$	(16,029	)
Net loss per share attributable to common stockholders,    basic and diluted	$	(0.39	)	$	(0.40	)	$	(0.39	)	$	(0.44	)