Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2017

Net Loss per Share

Basic and diluted net loss per common share

	Year ended December 31,
(in thousands, except per share data)	2017		2016		2015
Numerator:
Net loss used to compute net loss per share, basic	$	(136,314)	$	(95,765)	$	(70,275)
Less:  Remeasurement gain on warrant liability		(1,148)		—		—
Net loss used to compute net loss per share, diluted	$	(137,462)	$	(95,765)	$	(70,275)
Denominator:
Weighted-average common shares outstanding		53,312		51,667		27,687
Less:  Weighted-average unvested common shares subject to repurchase		—		(91)		(1,483)
Weighted-average number of shares used in computing net loss per share, basic		53,312		51,576		26,204
Add:  Incremental shares from assumed exercise of warrants		292		—		—
Weighted-average number of shares used in computing net loss per share, diluted		53,604		51,576		26,204
Net loss per share, basic	$	(2.56)	$	(1.86)	$	(2.68)
Net loss per share, diluted	$	(2.56)	$	(1.86)	$	(2.68)

Total outstanding potentially dilutive shares not included in the calculation of dilutive EPS

	As of December 31,
	2017	2016	2015
Options to purchase common stock	9,963	9,043	9,316
Warrants to purchase common stock	—	377	377
Restricted stock units	389	159	—
Employee stock purchase plan	79	90	—
Common stock subject to repurchase	—	—	1,307
	10,431	9,669	11,000