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Stock award plan - (Tables) | 6 Months Ended
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Jun. 30, 2021
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, 2020 |  | 9,663,677 | ​ | $ | 38.72 |  |  |  | ​ | ​ |
Granted |  | 2,282,914 | ​ | ​ | 63.38 |  |  |  | ​ | ​ |
Exercised |  | (475,942) | ​ | ​ | 27.66 |  |  |  | ​ | ​ |
Forfeited/Cancelled |  | (439,189) | ​ | ​ | 53.85 |  |  |  | ​ | ​ |
Outstanding at June 30, 2021 |  | 11,031,460 | ​ | $ | 43.70 |  | 7.34 | years | ​ | $ | 64,268
Vested or Expected to vest at June 30, 2021 |  | 5,192,055 | ​ | $ | 49.23 |  | 8.62 | years | ​ | $ | 16,236
Exercisable at June 30, 2021 |  | 5,255,302 | ​ | $ | 37.17 |  | 5.89 | years | ​ | $ | 47,129
​
Schedule of assumptions used to estimate fair values of grants made on the date of grant | ​
​ | ​ | ​
​ |  | Six months ended
​ |  | June 30, 2021
Risk-free interest rate |  | 0.51% - 0.96%
Expected volatility |  | 85.94% - 88.61%
Expected term |  | 5.5 years
Summary of information on the Company's restricted stock | ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Restricted Stock Awards and Units
​ | ​ | ​ | ​ | Weighted
​ | ​ | ​ | ​ | Average
​ | ​ | ​ | ​ | Grant
​ | ​ | Number of | ​ | Date
​ |  | Shares |  | Fair Value
Unvested at December 31, 2020 | ​ | 982,058 | ​ | $ | 41.78
Granted |  | 951,558 | ​ | ​ | 64.21
Vested |  | (319,127) | ​ | ​ | 35.21
Forfeited |  | (82,059) | ​ | ​ | 57.75
Unvested at June 30, 2021 |  | 1,532,430 | ​ | $ | 56.23
Schedule of share-based compensation expense recorded in the statement of operations | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended June 30, | ​ | Six Months Ended June 30, | ​
​ |  | 2021 |  | 2020 |  | 2021 |  | 2020 | ​
Research and development | ​ | $ | 13,443 | ​ | $ | 8,562 | ​ | $ | 27,168 | ​ | $ | 16,741 | ​
Selling, general and administrative | ​ |  | 12,256 | ​ |  | 8,348 | ​ |  | 24,238 | ​ |  | 15,389 | ​
Total | ​ | $ | 25,699 | ​ | $ | 16,910 | ​ | $ | 51,406 | ​ | $ | 32,130 | ​
​

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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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