Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Computation of Basic and Diluted Net Loss per Share

The following table sets forth the reconciliation of the numerator and denominator used in the computation of basic and diluted net loss per share for the years ended December 31, 2015, 2014 and 2013 (in thousands, except per share amounts):

	Year Ended December 31,
	2015			2014			2013
Numerator for Basic and Diluted:
Net loss used for basic calculation	$	(55,868	)	$	(38,755	)	$	(43,337	)
Effect of revaluation of warrant liability		(3,566	)		(7,708	)		—
Adjusted net loss used for dilution calculation	$	(59,434	)	$	(46,463	)	$	(43,337	)
Denominator:
Basic weighted average number of shares outstanding		96,068			74,767			67,569
Effect of dilutive potential shares		837			1,767			—
Diluted weighted average number of shares outstanding		96,905			76,534			67,569
Net loss per share:
Basic	$	(0.58	)	$	(0.52	)	$	(0.64	)
Diluted	$	(0.61	)	$	(0.61	)	$	(0.64	)

Anti-Dilutive Effect of Common Shares

The table below presents shares underlying stock options, employee stock purchase plan rights, warrants, restricted stock units and/or convertible preferred stock that were excluded from the calculation of the weighted average number of shares outstanding used for the calculation of diluted net loss per share. These were excluded from the calculation due to their anti-dilutive effect for the years ended December 31, 2015, 2014 and 2013 (shares in thousands):

	Year Ended December 31,
	2015		2014		2013
Weighted average number of anti-dilutive potential shares
Outstanding options		13,681		11,722		10,296
Warrants		—		—		6,074
Total		13,681		11,722		16,370