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Share-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
Summary of Incentive Unit Activity | The following table summarizes the Company’s incentive unit activity since December 31, 2016:
|  | Number of Units |  |  | Weighted Average Strike Price |  |  | Weighted Average Contractual Term |  |  | Aggregate Intrinsic Value |
|  |  |  |  |  |  |  |  |  | (in years) |  |  | (in thousands) |
Outstanding as of December 31, 2016 |  |  | 413,266 |  |  | $ | 2.75 |  |  |  | 9.1 |  |  | $ | 779 |
Granted |  |  | 9,132 |  |  |  | 1.28 |  |  |  | — |  |  |  | — |
Exercised |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Forfeited |  |  | (19,541 | ) |  |  | 4.99 |  |  |  | — |  |  |  | — |
Cancelled |  |  | (402,857 | ) |  |  | 2.62 |  |  |  | — |  |  |  | — |
Outstanding as of December 31, 2017 |  |  | — |  |  | $ | — |  |  |  | — |  |  | $ | — |
Summary of Assumptions used to determine Fair Value of Incentive Unit and Stock Option Awards Granted to Employees and Directors | The assumptions that the Company used in the Black-Scholes option-pricing model to determine the fair value of incentive unit and stock option awards granted to employees and directors were as follows, presented on a weighted average basis:
|  | Year Ended December 31, |
|  | 2017 |  |  | 2016 |  |  | 2015 |
Risk-free interest rate |  |  | 2.0 | % |  |  | 1.3 | % |  |  | 1.5 | %
Expected term (in years) |  |  | 6.1 |  |  |  | 6.3 |  |  |  | 6.3 |
Expected volatility |  |  | 77.1 | % |  |  | 76.5 | % |  |  | 62.6 | %
Expected dividend yield |  |  | 0.0 | % |  |  | 0.0 | % |  |  | 0.0 | %
Summary of Stock Option Activity | The following table summarizes stock option activity during 2017:
|  | Number of Shares |  |  | Weighted Average Exercise Price |  |  | Weighted Average Contractual Term |  |  | Aggregate Intrinsic Value |
|  |  |  |  |  |  |  |  |  | (in years) |  |  | (in thousands) |
Outstanding as of December 31, 2016 |  |  | — |  |  | $ | — |  |  |  | — |  |  | $ | — |
Granted |  |  | 2,012,106 |  |  |  | 7.24 |  |  |  | — |  |  |  | — |
Exercised |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Forfeited |  |  | (810 | ) |  |  | 5.90 |  |  |  | — |  |  |  | — |
Cancelled |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Outstanding as of December 31, 2017 |  |  | 2,011,296 |  |  | $ | 7.24 |  |  | 9.38 |  |  | $ | 9,074 |
Outstanding as of December 31, 2017 - vested and expected to vest |  |  | 2,011,296 |  |  | $ | 7.24 |  |  | 9.38 |  |  | $ | 9,074 |
Exercisable at December 31, 2017 |  |  | 357,494 |  |  | $ | 5.90 |  |  | 9.29 |  |  | $ | 2,091 |
Summary of Share-Based Compensation Expense | The Company recorded share-based compensation expense, for both incentive units and stock options in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):
|  | Year Ended December 31, |
|  | 2017 |  |  | 2016 |  |  | 2015 |
Research and development expenses |  | $ | 371 |  |  | $ | 66 |  |  | $ | 13 |
General and administrative expenses |  |  | 1,056 |  |  |  | 114 |  |  |  | 8 |
Total |  | $ | 1,427 |  |  | $ | 180 |  |  | $ | 21 |

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- Definition Tabular disclosure of the allocation of equity-based compensation costs to a given line item on the balance sheet and income statement for the period. This may include the reporting line for the costs and the amount capitalized and expensed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -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=27013229&loc=d3e301413-122809 + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=96867065&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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