Stock-Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2017 |
Share-based Compensation [Abstract] |
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Summary of Fair Value Assumptions for Stock Options |
The following table summarizes the grant date fair value and assumptions used in determining the fair value of all stock options granted, including grants of inducement options, during the years ended December 31, 2017, 2016 and 2015. | | | | | | | | 2017 | | 2016 | | 2015 | Volatility | 71% - 79% | | 74% - 77% | | 78% - 82% | Risk-free interest rate | 1.73% - 2.13% | | 1.00% - 1.90% | | 1.31% - 1.75% | Dividend yield | 0.0% | | 0.0% | | 0.0% | Expected option term (in years) | 6.25 | | 6.25 | | 6.25 | Weighted average fair value of stock options granted | $10.52 | | $8.77 | | $14.20 |
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Summary of Stock Option Activity |
The following table summarizes stock option activity for stock options granted for the years ended December 31, 2017, 2016 and 2015 as follows: | | | | | | | | | | | | | | | Number of Shares | | Weighted Average Exercise Price | | Weighted Average Remaining Contractual Life in Years | | Aggregate Intrinsic Value (in '000) | Options outstanding at January 1, 2015 | 4,400,106 |
| | $ | 10.59 |
| | | | |
| Granted | 1,902,850 |
| | 20.45 |
| | | | |
| Exercised | (481,140 | ) | | 10.62 |
| | | | |
| Forfeited and expired | (548,094 | ) | | 15.43 |
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| Options outstanding at December 31, 2015 | 5,273,722 |
| | $ | 13.64 |
| | | | |
| Vested and expected to vest at December 31, 2015 | 5,059,645 |
| | 13.46 |
| | | | |
| Exercisable at December 31, 2015 | 1,991,141 |
| | 8.70 |
| | | | |
| Options outstanding at December 31, 2015 | 5,273,722 |
| | $ | 13.64 |
| | | | |
| Granted | 2,532,675 |
| | 12.96 |
| | | | |
| Exercised | (162,340 | ) | | 6.68 |
| | | | |
| Forfeited and expired | (527,351 | ) | | 17.08 |
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| Options outstanding at December 31, 2016 | 7,116,706 |
| | $ | 13.30 |
| | | | |
| Vested and expected to vest at December 31, 2016 | 6,850,658 |
| | 13.25 |
| | | | |
| Exercisable at December 31, 2016 | 3,113,998 |
| | 11.28 |
| | | | |
| Options outstanding at December 31, 2016 | 7,116,706 |
| | $ | 13.30 |
| | | | |
| Granted | 2,284,710 |
| | 15.92 |
| | | | |
| Exercised | (378,275 | ) | | 9.08 |
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| Forfeited and expired | (414,220 | ) | | 15.50 |
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| Options outstanding at December 31, 2017 | 8,608,921 |
| | $ | 14.08 |
| | 7.4 | | $ | 147,260 |
| Vested and expected to vest at December 31, 2017 | 8,325,255 |
| | $ | 14.03 |
| | 7.4 | | $ | 142,783 |
| Exercisable at December 31, 2017 | 4,229,478 |
| | $ | 12.71 |
| | 6.3 | | $ | 78,138 |
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Summary of Exercise Price and Number of Stock Options Exercisable |
The following table summarizes the range of exercise prices and the number of stock options outstanding and exercisable as of December 31, 2017: | | | | | | | | | | | | | | | | | | | | | | | | Outstanding as of December 31, 2017 | | Exercisable as of December 31, 2017 | Range of Exercise Prices | | Number of Options | | Weighted Average Remaining Contractual Term (in years) | | Weighted Average Exercise Price | | Number of Options | | Weighted Average Exercise Price | $ | 3.03 |
| | $ | 4.55 |
| | 973,195 |
| | 4.65 | | $ | 3.60 |
| | 973,195 |
| | $ | 3.60 |
| $ | 6.90 |
| | $ | 6.90 |
| | 137,577 |
| | 5.22 | | $ | 6.90 |
| | 100,077 |
| | $ | 6.90 |
| $ | 6.96 |
| | $ | 10.85 |
| | 1,077,621 |
| | 8.29 | | $ | 10.76 |
| | 420,374 |
| | $ | 10.62 |
| $ | 11.14 |
| | $ | 12.58 |
| | 1,088,035 |
| | 6.39 | | $ | 12.17 |
| | 781,991 |
| | $ | 12.18 |
| $ | 12.66 |
| | $ | 13.67 |
| | 1,043,273 |
| | 8.74 | | $ | 13.59 |
| | 101,126 |
| | $ | 13.26 |
| $ | 13.94 |
| | $ | 15.91 |
| | 862,300 |
| | 7.76 | | $ | 14.97 |
| | 406,441 |
| | $ | 14.53 |
| $ | 16.07 |
| | $ | 16.16 |
| | 1,008,750 |
| | 7.69 | | $ | 16.13 |
| | 463,629 |
| | $ | 16.12 |
| $ | 16.35 |
| | $ | 17.24 |
| | 868,650 |
| | 9.24 | | $ | 17.13 |
| | 23,999 |
| | $ | 16.85 |
| $ | 17.36 |
| | $ | 22.76 |
| | 1,415,700 |
| | 7.14 | | $ | 21.18 |
| | 927,334 |
| | $ | 21.23 |
| $ | 22.84 |
| | $ | 31.78 |
| | 133,820 |
| | 8.86 | | $ | 27.47 |
| | 31,312 |
| | $ | 23.74 |
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Summary of RSU Activity |
The following table summarizes RSU awards granted during the years ended December 31, 2017, 2016 and 2015: | | | | | | | | | Number of RSUs | | Weighted Average Grant Price | Outstanding at January 1, 2015 | 20,502 |
| | $ | 19.47 |
| Granted | 49,776 |
| | 16.07 |
| Released | (26,724 | ) | | (18.68 | ) | Forfeited | — |
| | — |
| Outstanding at December 31, 2015 | 43,554 |
| | $ | 19.47 |
| Granted | 89,194 |
| | 10.85 |
| Released | (43,554 | ) | | (16.07 | ) | Forfeited | — |
| | — |
| Outstanding at December 31, 2016 | 89,194 |
| | $ | 10.85 |
| Granted | 46,914 |
| | 17.16 |
| Released | (89,194 | ) | | (10.85 | ) | Forfeited | — |
| | — |
| Outstanding at December 31, 2017 | 46,914 |
| | $ | 17.16 |
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Summary of Allocation of Employee Stock-Based Compensation |
The following table summarizes the stock-based compensation recorded in the Consolidated Statements of Comprehensive Loss related to stock options and RSUs during the years ended December 31, 2017, 2016 and 2015: | | | | | | | | | | | | | | 2017 | | 2016 | | 2015 | | (in millions) | Research and development expenses | $ | 6.5 |
| | $ | 6.2 |
| | $ | 4.0 |
| General and administrative expenses | 11.6 |
| | 11.8 |
| | 11.6 |
| Total (1) | $ | 18.1 |
| | $ | 18.0 |
| | $ | 15.6 |
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| | (1) | Includes $0.0 million, $1.7 million and $2.3 million for the years ended December 31, 2017, 2016 and 2015, respectively, for the remeasurement of certain stock options and RSUs that occurred during May 2013. |
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