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Stock award plan - (Tables) | 6 Months Ended
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Jun. 30, 2020
Share-based Payment Arrangement [Abstract] |
Summary of stock option activity | A summary of stock option activity is as follows:
|  | Number of options |  | Weighted- average exercise price |  | Weighted- average remaining contractual term |  | Aggregate intrinsic value (in thousands)
Outstanding at December 31, 2019 |  | 11,043,939 |  |  | $ | 31.67 |  |  |  |  |
Granted |  | 2,515,200 |  |  | $ | 50.98 |  |  |  |  |
Exercised |  | (1,034,288) |  |  | $ | 24.21 |  |  |  |  |
Forfeited/Cancelled |  | (570,167) |  |  | $ | 42.27 |  |  |  |  |
Outstanding at June 30, 2020 |  | 11,954,684 |  |  | $ | 35.84 |  |  | 7.48 years |  | $ | 183,488 |
Vested or Expected to vest at June 30, 2020 |  | 5,690,848 |  |  | $ | 39.16 |  |  | 8.86 years |  | $ | 66,986 |
Exercisable at June 30, 2020 |  | 5,512,252 |  |  | $ | 31.61 |  |  | 5.85 years |  | $ | 110,222 |
Schedule of assumptions used to estimate fair values of grants made on the date of grant | The fair value of grants made in the six months ended June 30, 2020 was contemporaneously estimated on the date of grant using the following assumptions:
|  | Six months ended June 30, 2020
Risk-free interest rate |  | 0.40% - 1.45%
Expected volatility |  | 87.50% - 89.31%
Expected term |  | 5.75 years
Summary of information on the Company's restricted stock | The following table summarizes information on the Company’s restricted stock awards and units:
|  | Restricted Stock Awards and Units |  |
|  | Number of Shares |  | Weighted Average Grant Date Fair Value
January 1, 2020 |  | 642,419 |  |  | $ | 24.50 |
Granted |  | 589,070 |  |  | $ | 49.67 |
Vested |  | (229,076) |  |  | $ | 23.53 |
Forfeited |  | (65,491) |  |  | $ | 36.11 |
Unvested at June 30, 2020 |  | 936,922 |  |  | $ | 39.97 |
Schedule of share-based compensation expense recorded in the statement of operations | The Company recorded share-based compensation expense in the statement of operations related to incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units and the ESPP as follows:
|  | Three Months Ended June 30, |  |  |  | Six Months Ended June 30, |  |
|  | 2020 |  | 2019 |  | 2020 |  | 2019
Research and development |  | $ | 8,562 |  |  | $ | 5,516 |  |  | $ | 16,741 |  |  | $ | 10,203 |
Selling, general and administrative |  | 8,348 |  |  | 5,404 |  |  | 15,389 |  |  | 9,981 |
Total |  | $ | 16,910 |  |  | $ | 10,920 |  |  | $ | 32,130 |  |  | $ | 20,184 |

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- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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