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Stock award plan - (Tables) | 9 Months Ended
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Sep. 30, 2020
Share-based Payment Arrangement [Abstract] |
Summary of stock option activity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Weighted- |  |  | ​ | ​
​ | ​ | ​ | ​ | Weighted- | ​ | average | ​ | ​ | Aggregate
​ | ​ | ​ | ​ | average | ​ | remaining | ​ | ​ | intrinsic
​ | ​ | Number of | ​ | exercise | ​ | contractual | ​ | ​ | value(in
​ | ​ | options | ​ | price | ​ | term | ​ | ​ | thousands)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |  | ​ | ​ | ​
Outstanding at December 31, 2019 |  | 11,043,939 | ​ | $ | 31.67 |  |  |  | ​ | ​ |
Granted |  | 2,671,660 | ​ | $ | 50.76 |  |  |  | ​ | ​ |
Exercised |  | (1,426,026) | ​ | $ | 23.14 |  |  |  | ​ | ​ |
Forfeited/Cancelled |  | (761,332) | ​ | $ | 42.96 |  |  |  | ​ | ​ |
Outstanding at September 30, 2020 |  | 11,528,241 | ​ | $ | 36.37 |  | 7.32 | years | ​ | $ | 138,286
Vested or Expected to vest at September 30, 2020 |  | 5,297,899 | ​ | $ | 40.09 |  | 8.70 | years | ​ | $ | 44,050
Exercisable at September 30, 2020 |  | 5,576,283 | ​ | $ | 32.19 |  | 5.84 | years | ​ | $ | 90,361
​
Schedule of assumptions used to estimate fair values of grants made on the date of grant | ​
​ | ​ | ​ | ​
​ |  | Nine months ended |
​ |  | September 30, 2020 |
Risk-free interest rate |  | 0.34% - 1.45% |
Expected volatility |  | 87.50% - 89.31% |
Expected term |  | 5.75 years |
Summary of information on the Company's restricted stock | ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Restricted Stock Awards and Units
​ | ​ | ​ | ​ | Weighted
​ | ​ | ​ | ​ | Average
​ | ​ | ​ | ​ | Grant
​ | ​ | Number of | ​ | Date
​ |  | Shares |  | Fair Value
January 1, 2020 | ​ | 642,419 | ​ | $ | 24.50
Granted |  | 625,390 | ​ | $ | 50.76
Vested |  | (232,263) | ​ | $ | 23.86
Forfeited |  | (73,751) | ​ | $ | 36.28
Unvested at September 30, 2020 |  | 961,795 | ​ | $ | 41.05
Schedule of share-based compensation expense recorded in the statement of operations | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended September 30, | ​ | Nine Months Ended September 30, | ​
​ |  | 2020 |  | 2019 |  | 2020 |  | 2019 | ​
Research and development | ​ | $ | 9,220 | ​ | $ | 4,988 | ​ | $ | 25,961 | ​ | $ | 15,191 | ​
Selling, general and administrative | ​ |  | 7,559 | ​ |  | 5,496 | ​ |  | 22,948 | ​ |  | 15,477 | ​
Total | ​ | $ | 16,779 | ​ | $ | 10,484 | ​ | $ | 48,909 | ​ | $ | 30,668 | ​
​

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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=120381028&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of allocation of amount expensed and capitalized for award under share-based payment arrangement to statement of income or comprehensive income and statement of financial position. Includes, but is not limited to, corresponding line item in financial statement. + 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 (h)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901 + 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=120381028&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=120381028&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=120381028&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=120381028&loc=d3e5070-113901 + Details
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