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Stock-Based Compensation (Tables) | 3 Months Ended
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Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
Schedule of Fair Value of Employee and Director Stock Options Estimated Using Weighted Average Assumptions | The fair value of employee and director stock options was estimated at the date of grant using a Black-Scholes option valuation model with the weighted average assumptions below.
|  | Three Months Ended March 31, |
|  | 2019 |  |  | 2018 |
Expected term (in years) |  |  | 6.1 |  |  |  | 6.1 |
Expected volatility |  |  | 45.0 | % |  |  | 45.9 | %
Risk-free interest rate |  |  | 2.40 | % |  |  | 2.72 | %
Dividend yield |  |  | 0.0 | % |  |  | 0.0 | %
Summary of Total Stock-Based Compensation Expense Included in Statements of Operations and Comprehensive Loss | The following table summarizes the total stock-based compensation expense included in the statements of operations and comprehensive loss for all periods presented (in thousands):
|  | Three Months Ended March 31, |
|  | 2019 |  |  | 2018 |
Cost of revenue |  | $ | 88 |  |  | $ | 117 |
Research and development |  |  | 873 |  |  |  | 576 |
Selling, general and administrative |  |  | 3,454 |  |  |  | 2,554 |
Total stock-based compensation expense |  | $ | 4,415 |  |  | $ | 3,247 |

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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://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=109197908&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=109197908&loc=d3e5047-113901 + 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=109197908&loc=d3e5070-113901 + Details
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