Net Loss Per Share Attributable to Common Stockholders

6 Months Ended

Jun. 30, 2013

Earnings Per Share [Abstract]

NET LOSS PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS

NET LOSS PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS

In April 2012, all of the Company’s then outstanding convertible preferred stock automatically converted into common stock in connection with its IPO. For periods that ended prior to the conversion, basic and diluted net income per common share were presented in conformity with the two-class method required for participating securities.

Under the two-class method, net loss is allocated between common shares and other participating securities to the extent that the securities are required to share in the losses. The Company’s convertible preferred stock did not meet the definition of a participating security in periods of net losses as the convertible preferred stockholders did not have a contractual obligation to share in the Company’s losses. Accordingly, net losses were attributable to common stockholders. Subsequent to the IPO and the automatic conversion of the outstanding convertible preferred stock, the Company had no other participating securities and the two-class method is no longer applicable.

Basic net loss per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average number of shares outstanding for the period. The disproportional change in loss per share for the six months ended June 30, 2013, as compared to the same period in the prior year, is attributed to the effect of the IPO of 10.3 million shares of its common stock. In addition, the IPO also effected the automatic conversion of the Company's convertible preferred stock and convertible notes into 28.7 million shares of its common stock.

Diluted net loss per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average number of common shares and potential dilutive common share equivalents outstanding during the period if the effect is dilutive. The Company’s potentially dilutive common shares include convertible notes and convertible preferred stock prior to their conversion, outstanding stock options and warrants, shares issuable pursuant to the ESPP and non-vested restricted stock units.

The following table presents the potential common shares outstanding that were excluded from the computation of diluted net loss per share attributable to common stockholders for the three and six months ended June 30, 2013 and 2012, respectively, because including them would have been anti-dilutive (in thousands):

	Three Months Ended June 30,		Six Months Ended June 30,
	2013	2012	2013	2012
Stock options to purchase common stock	7,878	7,191	7,893	8,126
Restricted stock units	358	42	303	125
Warrants to purchase common stock	312	331	322	331
Total	8,548	7,564	8,518	8,582