Stockholders' Equity | Stockholders' Equity Share-Based Compensation Total share-based compensation expense recorded for employees and non-employees, is as follows (in thousands): Three Months Ended Six Months Ended 2015 2014 2015 2014 Cost of revenues $ 81 $ 134 $ 215 $ 312 Technology and development 1,273 2,635 5,980 5,017 Sales and marketing 1,034 2,263 6,088 3,595 General and administrative 5,443 3,449 10,568 6,487 Total share-based compensation expense $ 7,831 $ 8,481 $ 22,851 $ 15,411 Fair Value of Stock Options We estimate the fair value of each stock option award using the Black-Scholes-Merton option-pricing model, which utilizes the estimated fair value of our common stock and requires input on the following subjective assumptions: Expected Term — The expected term for options granted to employees, officers, and directors is calculated as the midpoint between the vesting date and the end of the contractual term of the options. The expected term for options granted to consultants is determined using the remaining contractual life. Expected Volatility — The expected volatility is based on the average volatility of public companies within our peer group as our common stock has not been publicly trading for a long enough period to rely on our own expected volatility. Expected Dividends — The dividend assumption is based on our historical experience. To date we have not paid any dividends on our common stock. Risk-Free Interest Rate — The risk-free interest rate used in the valuation method is the implied yield currently available on the United States treasury zero-coupon issues, with a remaining term equal to the expected life term of our options. The following table summarizes the key assumptions used to determine the fair value of our stock options granted to employees, officers and directors: Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Expected term (years) 5.50 6.07 5.50 6.07 Expected volatility 50.68 % 55.91 % 50.68 % 56.15 % Dividend yield — % — % — % — % Risk-free interest rate 1.75 % 1.88 % 1.75 % 1.91 % Weighted-average grant-date fair value per share $ 3.63 $ 3.66 $ 3.63 $ 3.82 Fair Value of Restricted Stock Units (RSUs) and of Performance-Based Restricted Stock Units (PSUs) RSUs and PSUs are converted into shares of our common stock upon vesting on a one-for-one basis. Vesting of RSUs is subject to the employee’s continuing service to us, while vesting of PSUs is subject to our achievement of specified corporate financial performance objectives and also the employee's continuing service to us. The compensation expense related to RSUs and PSUs is determined using the fair value of our common stock on the date of grant and the expense is recognized on a straight-line basis over the vesting period. RSUs are typically fully vested at the end of three or four years while PSUs vest subject to the achievement of performance objectives and if achieved, typically vest over two to three years . We assess the achievement of performance objectives on a quarterly basis and adjust our share-based payment expense as appropriate. Fair Value of Employee Stock Purchase Plan Under the 2013 Employee Stock Purchase Plan (the 2013 ESPP), rights to purchase shares are generally granted during the second and fourth quarter of each year. The fair value of rights granted under the 2013 ESPP was estimated at the date of grant using the Black-Scholes-Merton option-pricing model. Stock Option Activity Option activity under our equity incentive plans was as follows: Options Outstanding Number of Options Outstanding Weighted- Average Exercise Price per Share Weighted-Average Remaining Contractual Term in Years Aggregate Intrinsic Value Balance at December 31, 2014 14,962,099 $ 8.53 7.11 $ 6,646,629 Granted 165,456 7.65 Exercised (1,646,852 ) 6.41 Canceled (661,730 ) 9.67 Balance at June 30, 2015 12,818,973 $ 8.74 6.88 $ 8,122,971 As of June 30, 2015 , our total unrecognized compensation expense for stock options granted to employees, officers, directors, and consultants was approximately $16.6 million , which will be recognized over a weighted-average vesting period of approximately 1.5 years . We recognize only the portion of the option award granted to employees that is ultimately expected to vest as compensation expense. Estimated forfeitures are determined based on historical data and management’s expectation of exercise behaviors. Forfeiture rates and the resulting compensation expense are revised in subsequent periods if actual forfeitures differ from the estimate. No option awards were granted to consultants during the three and six months ended June 30, 2015 and 2014 . Total share-based compensation expense for consultants was not significant for the three and six months ended June 30, 2015 and 2014 . There was no capitalized share-based compensation expense as of June 30, 2015 or 2014 . RSU and PSU Activity RSUs and PSUs Outstanding Number of RSUs and PSUs Outstanding Weighted Average Grant Date Fair Value Balance at December 31, 2014 9,125,190 $ 6.25 Granted 7,085,445 6.79 Released (2,320,865 ) 7.78 Canceled (596,939 ) 6.48 Balance at June 30, 2015 13,292,831 $ 6.26 During the three and six months ended June 30, 2014 , 29,502 and 1,285,261 RSUs granted prior to our initial public offering (IPO) vested and were settled for shares of our common stock, respectively. Of those shares, we withheld 10,859 and 527,778 shares valued at approximately $0.1 million and $3.6 million , respectively, in satisfaction of tax withholding obligations for employees who elected to net settle, i.e., surrender shares of common stock to satisfy their tax obligations. Payment of taxes related to this net share settlement of RSUs is reflected as a financing activity in our condensed consolidated statements of cash flows. The shares withheld by us as a result of the net settlement are no longer considered issued and outstanding, thereby reducing our shares outstanding used to calculate earnings per share. These shares are returned to the reserves and are available for future issuance under the 2013 Equity Incentive Plan (the 2013 Plan). In February 2015, we granted PSUs under the 2013 Plan to certain of our key employees. The PSUs entitle the employees to receive a certain number of shares of our common stock based on our satisfaction of certain financial and strategic performance targets during 2015 (the Performance Period). Based on the achievement of the performance conditions during the Performance Period for the February grants, the final settlement will range between zero and 100% of the target shares underlying the PSU awards based on a specified objective formula approved by the Compensation Committee. If earned, these PSUs will vest annually over a two or three year period depending on the employee, with the initial vesting in February 2016. The target number of shares underlying the PSUs that were granted to certain key employees during the six months ended June 30, 2015 totaled 2,300,824 shares and had a weighted average grant date fair value of $6.59 per share. No PSUs were granted in the three months ended June 30, 2015 . As of June 30, 2015 , 100% of the PSUs are expected to vest. As of June 30, 2015 , we had a total of approximately $53.9 million of unrecognized compensation costs related to RSUs and PSUs that is expected to be recognized over the remaining weighted average period of 1.8 years . |