Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

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, 2014, 2013 and 2012 (in thousands, except per share amounts):

	Year Ended December 31,
	2014			2013			2012
Numerator for Basic and Diluted:
Net loss used for basic calculation	$	(38,755	)	$	(43,337	)	$	(15,917	)
Effect of revaluation of warrant liability		(7,708	)		0			(2,059	)
Adjusted net loss used for dilution calculation	$	(46,463	)	$	(43,337	)	$	(17,976	)
Denominator:
Basic weighted average number of shares outstanding		74,767			67,569			54,515
Effect of dilutive potential shares		1,767			0			546
Diluted weighted average number of shares outstanding		76,534			67,569			55,061
Net loss per share:
Basic	$	(0.52	)	$	(0.64	)	$	(0.29	)
Diluted	$	(0.61	)	$	(0.64	)	$	(0.33	)

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, 2014, 2013 and 2012 (shares in thousands):

	Year Ended December 31,
	2014		2013		2012
Weighted average number of anti-dilutive potential shares		11,722		16,370		8,716