| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | Period [Axis] |
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2016-01-01 - 2016-12-31 |
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Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |
Summary of Stock-based Compensation | A summary of our stock-based compensation expense is as follows (in thousands): | | | | | | | | | | | | | | Years Ended December 31, | | 2016 | | 2015 | | 2014 | Stock-based compensation by type of award: | | | | | | Stock options | $ | 4,153 |
| | $ | 5,565 |
| | $ | 5,852 |
| Restricted stock units | 12,567 |
| | 8,871 |
| | 3,217 |
| Employee stock purchase rights | 202 |
| | 2,425 |
| | 3,290 |
| | $ | 16,922 |
| | $ | 16,861 |
| | $ | 12,359 |
| | | | | | | Stock-based compensation by category of expense: | | | | | | Cost of revenue | $ | 1,105 |
| | $ | 1,533 |
| | $ | 1,063 |
| Sales and marketing | 7,006 |
| | 7,735 |
| | 5,829 |
| Research and development | 5,732 |
| | 5,437 |
| | 3,932 |
| General and administrative | 3,079 |
| | 2,156 |
| | 1,535 |
| | $ | 16,922 |
| | $ | 16,861 |
| | $ | 12,359 |
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ESPP Valuation Assumptions | The fair values of the options and employee stock purchase rights are estimated as of the grant date using the Black-Scholes option-pricing model with the following assumptions:
| | | | | | | | | | | | | | Options | | Employee Stock Purchase Rights | | Years Ended December 31, | | Years Ended December 31, | | 2016 | | 2015 | | 2014 | | 2016 | | 2015 | | 2014 | Expected term (in years) | 4.9 | | 4.8 | | 4.8 | | 1.3 | | 1.3 | | 1.3 | Risk-free interest rate | 1.4% | | 1.6% | | 1.8% | | 0.8% | | 0.5% | | 0.3% | Expected volatility | 49% | | 50% | | 41% | | 42% | | 41% | | 27% | Dividend rate | —% | | —% | | —% | | —% | | —% | | —% |
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Stock Options Valuation Assumptions | The fair values of the options and employee stock purchase rights are estimated as of the grant date using the Black-Scholes option-pricing model with the following assumptions:
| | | | | | | | | | | | | | Options | | Employee Stock Purchase Rights | | Years Ended December 31, | | Years Ended December 31, | | 2016 | | 2015 | | 2014 | | 2016 | | 2015 | | 2014 | Expected term (in years) | 4.9 | | 4.8 | | 4.8 | | 1.3 | | 1.3 | | 1.3 | Risk-free interest rate | 1.4% | | 1.6% | | 1.8% | | 0.8% | | 0.5% | | 0.3% | Expected volatility | 49% | | 50% | | 41% | | 42% | | 41% | | 27% | Dividend rate | —% | | —% | | —% | | —% | | —% | | —% |
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Summary of Activity under Stock Option Plans | The following table summarizes our stock option activities and related information:
| | | | | | | | | | | | | | | | | Number of Shares (thousands) | | Weighted-Average Exercise Price | | Weighted-Average Remaining Contractual Term (Years) | | Aggregate Intrinsic Value (thousands) | Outstanding as of December 31, 2015 | | 9,291 |
| | $ | 4.78 |
| | | | | Granted | | 672 |
| | $ | 5.52 |
| | | | | Exercised | | (1,444 | ) | | $ | 4.22 |
| | | | | Canceled (1) | | (651 | ) | | $ | 6.23 |
| | | | |
| Outstanding as of December 31, 2016 | | 7,868 |
| | $ | 4.82 |
| | 6.2 | | $ | 28,931 |
| Vested and expected to vest as of December 31, 2016 | | 7,758 |
| | $ | 4.82 |
| | 6.2 | | $ | 28,554 |
| Vested and exercisable as of December 31, 2016 | | 5,688 |
| | $ | 4.57 |
| | 5.6 | | $ | 22,363 |
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_____________________________________ (1) Common shares subject to awards granted under the 2008 Plan and canceled after March 21, 2014 are reallocated to the 2014 Plan’s share reserve and become available for issuance under the 2014 Plan. During the years ended 2016 and 2015, 266,799 shares and 1,640,324 shares of the canceled stock options, respectively, were reallocated and became available for issuance under the 2014 Plan. |
Stock Option Information | The following table provides information pertaining to our stock options (in thousands, except weighted-average fair values): | | | | | | | | | | | | | | Years Ended December 31, | | 2016 | | 2015 | | 2014 | Fair value of options granted | $ | 1,603 |
| | $ | 869 |
| | $ | 11,683 |
| Weighted-average fair value of options granted | $ | 2.38 |
| | $ | 2.13 |
| | $ | 2.79 |
| Intrinsic value of options exercised | $ | 5,990 |
| | $ | 2,299 |
| | $ | 14,863 |
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Summary of Restricted Stock Units Activity | The following table summarizes our stock award activities and related information: | | | | | | | | | | | | | | | Number of Shares (thousands) | | Weighted Average Grant Date Fair Value | | Weighted-Average Remaining Vesting Term (Years) | | Aggregate Intrinsic Value (thousands) | Outstanding as of December 31, 2015 | 3,452 |
| | $ | 5.88 |
| | | | | Granted | 4,550 |
| | $ | 6.50 |
| | | | | Released | (1,139 | ) | | $ | 8.16 |
| | | | | Canceled | (904 | ) | | $ | 6.56 |
| | | | | Outstanding as of December 31, 2016 | 5,959 |
| | $ | 5.81 |
| | 1.6 | | $ | 49,517 |
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