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Stock-based Compensation (Tables) | 9 Months Ended
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Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
Weighted Average Assumptions | The fair value of the stock options granted during the three and nine months ended September 30, 2019 and 2018, was estimated based on the following weighted average assumptions:
| Three Months Ended September 30, |  |  | Nine Months Ended September 30, |
| 2019 |  |  | 2018 |  |  | 2019 |  |  | 2018 |
Dividend yield |  | 0 | % |  |  | 0 | % |  |  | 0 | % |  |  | 0 | %
Expected volatility |  | 101 | % |  |  | 101 | % |  |  | 103 | % |  |  | 101 | %
Risk-free interest rate |  | 1.71 | % |  |  | 2.76 | % |  |  | 2.49 | % |  |  | 2.72 | %
Expected term | 5.47 years |  |  | 5.60 years |  |  | 5.60 years |  |  | 5.60 years |
Stock Option Activity | Stock option activity for the nine months ended September 30, 2019, was as follows:
| Number of shares |  |  | Weighted Average Exercise Price Per Share |  |  | Weighted Average Remaining Contractual Term (in years) |  |  | Aggregate Intrinsic Value (in thousands) |
Outstanding at beginning of year |  | 1,624,746 |  |  | $ | 23.09 |  |  |  |  |  |  |  |  |
Granted |  | 400,814 |  |  |  | 14.49 |  |  |  |  |  |  |  |  |
Exercised |  | (50,513 | ) |  |  | 4.86 |  |  |  |  |  |  |  |  |
Forfeited, expired or cancelled |  | (165,432 | ) |  |  | 33.83 |  |  |  |  |  |  |  |  |
Outstanding at end of period |  | 1,809,615 |  |  | $ | 20.71 |  |  |  | 7.05 |  |  | $ | 16,127 |
Exercisable at end of period |  | 1,347,408 |  |  | $ | 23.16 |  |  |  | 6.47 |  |  | $ | 12,921 |
Stock-based Compensation Expense | The following table shows total stock-based compensation expense for stock options, RSUs and ESPP in the condensed consolidated statements of operations and comprehensive income (loss) (in thousands):
| Three Months Ended September 30, |  |  | Nine Months Ended September 30, |
| 2019 |  |  | 2018 |  |  | 2019 |  |  | 2018 |
Research and development | $ | 66 |  |  | $ | 97 |  |  | $ | 174 |  |  | $ | 296 |
General and administrative |  | 1,428 |  |  |  | 750 |  |  |  | 4,059 |  |  |  | 2,737 |
Total stock-based compensation expense | $ | 1,494 |  |  | $ | 847 |  |  | $ | 4,233 |  |  | $ | 3,033 |

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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=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 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=116856206&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=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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