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v3.20.4

Stockholders' Equity (Tables) | 12 Months Ended
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Dec. 31, 2020
Equity [Abstract] |
Schedule of Share-Based Compensation Expense | The following table summarizes non-cash share-based compensation expense (in thousands):
| December 31,
| 2020 |  | 2019 |  | 2018
Share-based compensation expense as a component of: |  |  |  |  |
Research and development expenses | $ | 13,497 |  |  | $ | 9,641 |  |  | $ | 8,352 |
General and administrative expenses | 17,230 |  |  | 14,874 |  |  | 12,494 |
| $ | 30,727 |  |  | $ | 24,515 |  |  | $ | 20,846 |
Schedule of Stock Option Plan Activity | Following is a summary of our stock option plan activity and related information:
| Shares |  | Weighted Average Exercise Price |  | Weighted Average Remaining Contractual Term in Years |  | Aggregate Intrinsic Value (In thousands)
Balance at January 1, 2018 | 1,876,332 |  |  | $ | 53.17 |  |  | 5.77 |  | $ | 157,340 |
Granted | 228,362 |  |  | $ | 162.00 |  |  |  |  |
Exercised | (358,162) |  |  | $ | 55.24 |  |  |  |  |
Forfeited | (10,228) |  |  | $ | 114.53 |  |  |  |  |
Balance at December 31, 2018 | 1,736,304 |  |  | $ | 66.71 |  |  | 5.47 |  | 125,858 |
Exercisable at December 31, 2018 | 1,313,374 |  |  | $ | 47.03 |  |  | 4.56 |  | 117,314 |
Options vested and expected to vest as of December 31, 2018 | 1,736,304 |  |  | $ | 66.71 |  |  | 5.47 |  | $ | 125,858 |
Granted | 338,617 |  |  | $ | 116.69 |  |  |  |  |
Exercised | (112,011) |  |  | $ | 23.65 |  |  |  |  |
Forfeited | (6,531) |  |  | $ | 139.37 |  |  |  |  |
Balance at December 31, 2019 | 1,956,379 |  |  | $ | 77.54 |  |  | 5.45 |  | 72,002 |
Exercisable at December 31, 2019 | 1,454,726 |  |  | $ | 61.82 |  |  | 4.42 |  | 70,345 |
Options vested and expected to vest as of December 31, 2019 | 1,956,379 |  |  | $ | 77.54 |  |  | 5.45 |  | $ | 72,002 |
Granted | 806,300 |  |  | $ | 92.93 |  |  |  |  |
Exercised | (156,845) |  |  | $ | 21.26 |  |  |  |  |
Forfeited | (44,012) |  |  | $ | 91.30 |  |  |  |  |
Balance at December 31, 2020 | 2,561,822 |  |  | $ | 85.59 |  |  | 6.09 |  | 59,033 |
Exercisable at December 31, 2020 | 1,611,830 |  |  | $ | 76.05 |  |  | 4.54 |  | 53,286 |
Options vested and expected to vest as of December 31, 2020 | 2,561,822 |  |  | $ | 85.59 |  |  | 6.09 |  | $ | 59,033 |
Schedule of Stock Option Plan Activity by Exercise Price Range | Following is a further breakdown of the options outstanding as of December 31, 2020:
Range of exercise prices | Options outstanding |  | Weighted average remaining life in years |  | Weighted average exercise price |  | Options exercisable |  | Weighted average exercise price
$10.05-$14.47 | 284,184 |  |  | 0.86 |  | $ | 13.08 |  |  | 270,184 |  |  | $ | 13.00 |
$21.92-$56.26 | 344,629 |  |  | 2.88 |  | $ | 35.34 |  |  | 344,629 |  |  | $ | 35.34 |
$63.58-$74.42 | 307,356 |  |  | 5.20 |  | $ | 71.96 |  |  | 220,650 |  |  | $ | 73.41 |
$82.90-$95.35 | 185,033 |  |  | 6.23 |  | $ | 86.22 |  |  | 140,400 |  |  | $ | 86.32 |
$95.68 | 305,106 |  |  | 9.12 |  | $ | 95.68 |  |  | 63,059 |  |  | $ | 95.68 |
$97.92 | 4,976 |  |  | 5.02 |  | $ | 97.92 |  |  | 4,976 |  |  | $ | 97.92 |
$98.20 | 270,850 |  |  | 9.26 |  | $ | 98.20 |  |  | — |  |  | $ | 98.20 |
$100.02-$113.76 | 257,914 |  |  | 6.69 |  | $ | 104.12 |  |  | 220,092 |  |  | $ | 103.96 |
$117.58 | 19,744 |  |  | 9.44 |  | $ | 117.58 |  |  | — |  |  | $ | 117.58 |
$117.97-$195.91 | 582,030 |  |  | 7.56 |  | $ | 137.18 |  |  | 347,840 |  |  | $ | 141.38 |
| 2,561,822 |  |  | 6.09 |  | $ | 85.59 |  |  | 1,611,830 |  |  | $ | 76.05 |
Schedule of Stock Option Weighted-Average Assumptions | The assumptions used for the specified reporting periods and the resulting estimates of weighted-average grant date fair value per share of options granted:
| Year Ended December 31,
| 2020 |  | 2019 |  | 2018 |
Risk-free interest rate | 0.2%-1.4% |  | 1.4%-2.6% |  | 2.7%-3.0% |
Expected volatility | 47%-71% |  | 40%-49% |  | 33%-36% |
Expected term | 4.7 to 5.1 years |  | 4.6 to 5.9 years |  | 5.1 to 5.8 years |
Schedule of Restricted Stock Activity | The following is a summary of our restricted stock activity and related information:
| Shares |  | Weighted-Average Grant Date Fair Value
Outstanding at January 1, 2018 | 133,294 |  |  | $ | 91.60 |
Granted | 62,133 |  |  | $ | 169.92 |
Vested | (61,989) |  |  | $ | 86.19 |
Forfeited | (1,165) |  |  | $ | 125.16 |
Outstanding at December 31, 2018 | 132,273 |  |  | $ | 130.63 |
Granted | 118,498 |  |  | $ | 115.90 |
Vested | (102,846) |  |  | $ | 121.55 |
Forfeited | (666) |  |  | $ | 134.36 |
Outstanding at December 31, 2019 | 147,259 |  |  | $ | 125.11 |
Granted | 111,306 |  |  | $ | 89.73 |
Vested | (52,363) |  |  | $ | 121.69 |
Forfeited | — |  |  | $ | — |
Outstanding at December 31, 2020 | 206,202 |  |  | $ | 106.88 |

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