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Employee Stock and Benefit Plans (Tables)
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12 Months Ended |
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Dec. 31, 2014
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| Share-based Compensation [Abstract] |
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| Stock-based employee compensation |
Stock-based employee compensation is included in the consolidated statements of operations as follows: | | | | | | | | | | | | | | | | Year Ended December 31, | | | 2014 | | 2013 | | 2012 | | | (in thousands) | Cost of revenues | | $ | 757 |
| | $ | 421 |
| | $ | 272 |
| Research and development | | 2,463 |
| | 1,038 |
| | 649 |
| Sales and marketing | | 2,394 |
| | 1,244 |
| | 993 |
| General and administrative | | 4,217 |
| | 1,842 |
| | 1,008 |
| Total stock-based employee compensation | | $ | 9,831 |
| | $ | 4,545 |
| | $ | 2,922 |
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| Fair value assumptions of options granted to employees |
The fair value of each option granted to employees is estimated on the date of grant using the Black-Scholes option-pricing model based on the following assumptions:
| | | | | | | | | | Year Ended December 31, | | | 2014 | | 2013 | | 2012 | Expected term (in years) | | 5.3 to 5.9 | | 5.4 to 6.1 | | 5.3 to 6.1 | Volatility | | 48% to 52% | | 52% to 53% | | 52% to 53% | Risk-free interest rate | | 1.5% to 1.7% | | 0.7% to 1.5% | | 0.6% to 0.9% | Dividend yield | | — | | — | | — |
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| Stock option activity |
A summary of the Company’s stock option activity is as follows: | | | | | | | | | | | | | | | | | Outstanding Shares | | Weighted Average Exercise Price | | Weighted Average Remaining Contractual Life (Years) | | Aggregate Intrinsic Value | | | | | | | | | (in thousands) | Balance as of December 31, 2011 | | 6,312,041 |
| | $ | 3.36 |
| | 6.9 | | $ | 16,012 |
| Granted | | 1,478,781 |
| | 8.94 |
| | | | | Exercised | | (724,316 | ) | | 2.86 |
| | | | | Canceled | | (552,998 | ) | | 6.79 |
| | | | | Balance as of December 31, 2012 | | 6,513,508 |
| | 4.39 |
| | 6.6 | | 67,711 |
| Granted | | 2,001,400 |
| | 15.78 |
| | | | | Exercised | | (952,871 | ) | | 4.32 |
| | | | | Canceled | | (522,944 | ) | | 10.71 |
| | | | | Balance as of December 31, 2013 | | 7,039,093 |
| | 7.17 |
| | 6.5 | | 112,312 |
| Granted | | 2,744,150 |
| | 26.16 |
| | | | | Exercised | | (1,216,710 | ) | | 6.28 |
| | | | | Canceled | | (961,126 | ) | | 16.91 |
| | | | | Balance as of December 31, 2014 | | 7,605,407 |
| | 12.93 |
| | 6.5 | | 188,743 |
| Vested and expected to vest—December 31, 2014 | | 6,931,052 |
| | 11.87 |
| | 6.2 | | 179,352 |
| Exercisable—December 31, 2014 | | 4,598,180 |
| | 5.68 |
| | 5.0 | | 146,714 |
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| Schedule of exercise price range, outstanding and vested |
The following table summarizes the outstanding and vested stock options at December 31, 2014: | | | | | | | | | | | | | | | | | | | | Outstanding | | Vested | Exercise Price | | Number of
Shares | | Weighted
Average
Exercise
Price Per
Share | | Weighted
Average
Remaining
Contractual
Life (Years) | | Number of
Shares | | Weighted
Average
Exercise
Price Per
Share | $1.00 - $1.50 | | 238,559 |
| | $ | 1.40 |
| | 1.5 | | 238,559 |
| | $ | 1.40 |
| $1.90 - $1.90 | | 941,482 |
| | 1.90 |
| | 2.1 | | 941,482 |
| | 1.90 |
| $2.10 - $2.80 | | 461,758 |
| | 2.62 |
| | 3.9 | | 461,758 |
| | 2.62 |
| $3.80 - $3.80 | | 1,148,568 |
| | 3.80 |
| | 4.8 | | 1,126,625 |
| | 3.80 |
| $4.10 - $8.40 | | 924,121 |
| | 5.55 |
| | 6.0 | | 826,292 |
| | 5.35 |
| $8.90 - $12.68 | | 846,930 |
| | 11.20 |
| | 7.9 | | 392,645 |
| | 10.93 |
| $13.50 - $20.80 | | 962,889 |
| | 18.50 |
| | 8.5 | | 250,599 |
| | 17.03 |
| $22.31 - $23.51 | | 383,050 |
| | 23.28 |
| | 9.6 | | 45,009 |
| | 22.55 |
| $26.86 - $26.86 | | 701,350 |
| | 26.86 |
| | 9.0 | | 29,728 |
| | 26.86 |
| $30.58 - $30.58 | | 996,700 |
| | 30.58 |
| | 9.4 | | 66,927 |
| | 30.58 |
| | | 7,605,407 |
| | 12.93 |
| | 6.5 | | 4,379,624 |
| | 5.58 |
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