Employee Stock and Benefit Plans (Tables)
|
12 Months Ended |
Dec. 31, 2015 |
| Share-based Compensation [Abstract] |
|
| Stock-based employee compensation |
Stock-based compensation for employee stock options is included in the consolidated statements of operations as follows: | | | | | | | | | | | | | | | | Year Ended December 31, | | | 2015 | | 2014 | | 2013 | | | (in thousands) | Cost of revenues | | $ | 1,250 |
| | $ | 757 |
| | $ | 421 |
| Research and development | | 4,936 |
| | 2,463 |
| | 1,038 |
| Sales and marketing | | 3,867 |
| | 2,394 |
| | 1,244 |
| General and administrative | | 6,325 |
| | 4,217 |
| | 1,842 |
| Total stock-based employee compensation | | $ | 16,378 |
| | $ | 9,831 |
| | $ | 4,545 |
|
|
| 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, | | | 2015 | | 2014 | | 2013 | Expected term (in years) | | 4.9 to 5.9 | | 5.3 to 5.9 | | 5.4 to 6.1 | Volatility | | 45% to 48% | | 48% to 52% | | 52% to 53% | Risk-free interest rate | | 1.3% to 1.7% | | 1.5% to 1.7% | | 0.7% to 1.5% | Dividend yield | | — | | — | | — |
|
| 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, 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 |
| Granted | | 1,526,450 |
| | 39.50 |
| | | | | Exercised | | (807,846 | ) | | 12.50 |
| | | | | Canceled | | (744,953 | ) | | 27.67 |
| | | | | Balance as of December 31, 2015 | | 7,579,058 |
| | 16.88 |
| | 5.9 | | 131,345 |
| Vested and expected to vest—December 31, 2015 | | 7,111,282 |
| | 15.69 |
| | 5.7 | | 130,208 |
| Exercisable—December 31, 2015 | | 5,195,339 |
| | 9.78 |
| | 4.8 | | 121,098 |
|
|
| Schedule of exercise price range, outstanding and vested |
The following table summarizes the outstanding and vested stock options at December 31, 2015: | | | | | | | | | | | | | | | | | | | | 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 | $1.40 - $1.40 | | 156,259 |
| | $ | 1.40 |
| | 0.5 | | 156,259 |
| | $ | 1.40 |
| $1.90 - $1.90 | | 940,082 |
| | 1.90 |
| | 1.1 | | 940,082 |
| | 1.90 |
| $2.10 - $2.80 | | 415,220 |
| | 2.63 |
| | 2.9 | | 415,220 |
| | 2.63 |
| $3.80 - $3.80 | | 1,117,235 |
| | 3.80 |
| | 3.9 | | 1,117,235 |
| | 3.80 |
| $4.10 - $8.90 | | 868,867 |
| | 6.16 |
| | 5.4 | | 842,958 |
| | 6.08 |
| $9.40 - $16.68 | | 786,624 |
| | 13.13 |
| | 6.9 | | 606,364 |
| | 12.95 |
| $19.26 - $26.86 | | 1,156,772 |
| | 24.00 |
| | 8.1 | | 575,066 |
| | 23.69 |
| $30.58 - $30.58 | | 827,997 |
| | 30.58 |
| | 8.7 | | 423,645 |
| | 30.58 |
| $34.97 - $37.28 | | 824,344 |
| | 36.31 |
| | 8.7 | | 14,381 |
| | 37.18 |
| $40.68 - $52.14 | | 485,658 |
| | 45.13 |
| | 8.9 | | 75,635 |
| | 41.39 |
| | | 7,579,058 |
| | 16.88 |
| | 5.9 | | 5,166,845 |
| | 9.79 |
|
|