Stock-Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2019 |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Summary of stock option activity |
| | | | | | | | | | | | | | | | Outstanding Options | | | | | | | | | | Weighted- | | | | | | | | | | Weighted- | | Average | | | | | | Shares | | | | Average | | Remaining | | Aggregate | | | | Available for | | Number of | | Exercise | | Contractual | | Intrinsic | | (in thousands, except for contractual life and exercise price) | | Grant | | Shares | | Price | | Life | | Value | | | | | | | | | | | (In years) | | | | Balance at December 31, 2018 | | 5,431 | | 9,463 | | $ | 7.69 | | 6.91 | | $ | 61,718 | | Additional shares authorized | | 2,483 | | — | | $ | — | | | | | | | Options granted | | (1,838) | | 1,838 | | $ | 18.01 | | | | | | | Options exercised | | — | | (2,464) | | $ | 5.29 | | | | | | | Options forfeited | | 340 | | (340) | | $ | 13.13 | | | | | | | Balance at December 31, 2019 | | 6,416 | | 8,497 | | $ | 10.39 | | 6.88 | | $ | 197,955 | | Exercisable at December 31, 2019 | | | | 4,835 | | $ | 7.27 | | 5.56 | | $ | 127,753 | | Vested and expected to vest at December 31, 2019 | | | | 8,288 | | $ | 10.29 | | 6.83 | | $ | 193,940 | |
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| Summary of offering activity |
| | | | | | | | Number of | | Total | | | Shares Purchased | | Proceeds | Offering Period | | | | | (in thousands) | November 1, 2017 - April 30, 2018 | | 206,447 | | $ | 1,855 | May 1, 2018 - October 31, 2018 | | 184,825 | | $ | 1,763 | November 1, 2018 - April 30, 2019 | | 132,177 | | $ | 2,147 | May 1, 2019 - October 31, 2019 | | 136,084 | | $ | 2,176 |
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| Restricted stock units |
| | | | | | | | | | Weighted- | | | | | Average | | | Number of | | Grant Date | | | Shares | | Fair Value | | | | | | | Balance at December 31, 2018 | | 1,084 | | $ | 11.72 | Granted | | 2,019 | | $ | 20.97 | Vested | | (541) | | $ | 12.56 | Canceled/Forfeited | | (158) | | $ | 16.68 | Balance at December 31, 2019 | | 2,404 | | $ | 19.86 | | | | | | |
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| Summary of stock-based compensation expenses |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Year ended December 31, | | | | 2019 | | 2018 | | 2017 | | | | Employee | | Non-Employee | | Total | | Employee | | Non-Employee | | Total | | Employee | | Non-Employee | | Total | | | | (in thousands) | | Cost of revenues | | $ | 905 | | $ | 32 | | ` | 937 | | $ | 564 | | $ | 5 | | $ | 569 | | $ | 544 | | $ | — | | $ | 544 | | Research and development | | | 5,354 | | | — | | | 5,354 | | | 4,043 | | | — | | | 4,043 | | | 3,214 | | | — | | | 3,214 | | Selling, general and administrative | | | 21,730 | | | 603 | | | 22,333 | | | 9,474 | | | 112 | | | 9,586 | | | 7,644 | | | — | | | 7,644 | | Total | | $ | 27,989 | | $ | 635 | | $ | 28,624 | | $ | 14,081 | | $ | 117 | | $ | 14,198 | | $ | 11,402 | | $ | — | | $ | 11,402 | |
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| Performance-based awards |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Schedule of assumptions used in valuation of fair value of employee stock options |
| | | | December 31, | | 2019 | Risk-free interest rate | | 1.63% – 2.61% | Expected dividend yield | | — | Expected volatility | | 50.00% | Expected term (years) | | 7.25 |
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| Employee stock options |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Schedule of assumptions used in valuation of fair value of employee stock options |
| | | | | | | | | | | | | | | | | | | | | Year ended December 31, | | | 2019 | | | 2018 | | | 2017 | | Expected term (years) | | 5.23 | | — | 10.00 | | | 5.24 | | — | 5.62 | | | 5.14 | | — | 5.24 | | Expected volatility | | 42.53 | % | — | 45.84 | % | | 40.28 | % | — | 42.53 | % | | 40.75 | % | — | 62.93 | % | Expected dividend rate | | | | | 0 | % | | | | | 0 | % | | | | | 0 | % | Risk-free interest rate | | 1.60 | % | — | 2.60 | % | | 2.37 | % | — | 3.06 | % | | 1.67 | % | — | 2.16 | % |
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| Non-employee stock options |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Schedule of assumptions used in valuation of fair value of employee stock options |
| | | | | | | | | | | | | | | Year ended December 31, | | | 2018 | | | 2017 | | Expected term (years) | | 2.72 | | — | 2.76 | | | 2.67 | | — | 2.71 | | Expected volatility | | 41.36 | % | — | 43.84 | % | | 41.22 | % | — | 52.18 | % | Expected dividend rate | | | | | 0 | % | | | | | 0 | % | Risk-free interest rate | | 2.36 | % | — | 2.86 | % | | 1.42 | % | — | 1.95 | % |
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