Stock-Based Compensation	9 Months Ended
Sep. 30, 2019
Stock-Based Compensation [Abstract]
Stock-Based Compensation	Note 5 — Stock-Based Compensation We have a stock incentive plan for employees and others called the VirnetX Holding Corporation 2013 Equity Incentive Plan (the “Plan”), which has been approved by our stockholders. In April 2017, the Board approved an amendment and restatement of the Plan to, among other things, increase the shares reserved under the Plan by 2,500,000 shares (the “Plan Amendment”). Our stockholders approved of the Plan Amendment at the 2017 Annual Meeting of Stockholders held on June 1, 2017. The Plan provides for grants of 16,624,469 shares of our common stock, including stock options and restricted stock units (“RSUs”), and will expire in 2023. As of September 30, 2019, 1,128,903 shares remained available for grant under the Plan. During the three months ended September 30, 2019, we did not grant any options. During the three months ended September 30, 2018, we granted options totaling 85,000 shares with a weighted average grant date fair value of $3.16. During the nine months ended September 30, 2019, we granted options for a total of 345,000 shares. The weighted average fair value at the grant dates for options issued during the nine months ended September 30, 2019 was $4.63 per option. The fair values of options at the grant date were estimated utilizing the Black-Scholes valuation model with the following weighted average assumptions for the nine months ended September 30, 2019 (i) dividend yield on our common stock of 0 percent (ii) expected stock price volatility of 92 percent (iii) a risk-free interest rate of 2.09 percent and (iv) an expected option term of 6 years. During the nine months ended September 30, 2018, we granted options for a total of 1,095,000 shares with a weighted average grant date fair value of $2.58. The fair values of options at the grant date were estimated utilizing the Black-Scholes valuation model with the following weighted average assumptions for the nine months ended September 30, 2018 (i) dividend yield on our common stock of 0 percent (ii) expected stock price volatility of 84 percent (iii) a risk-free interest rate average of 2.73 percent and (iv) an expected option term of 6 years. During the three months ended September 30, 2019 and 2018, we did not grant any RSUs. During the nine months ended September 30, 2019 and 2018, we granted 229,996 and 243,997 RSUs, respectively. The weighted average fair values at the grant dates for RSUs issued during the nine months ended September 30, 2019 and 2018 were $6.06 and $3.26 per RSU, respectively. RSUs, which are subject to forfeiture if service terminates prior to the shares vesting, are expensed ratably over the vesting period. During the nine months ended September 30, 2019 and 2018, we paid $47 and $42 in withholding taxes on shares issued upon conversion of RSUs. The underlying shares were canceled. These amounts are reflected as financing costs in the accompanying condensed consolidated statements of cash flows. Stock-based compensation expense included in general and administrative expense was $565 and $1,437 and in research and development expense was $434 and $1,275 for the three and nine months ended September 30, 2019, respectively, and $592 and $1,447 for general and administrative expense and $425 and $1,580 for research and development expense for the three and nine months ended September 30, 2018, respectively. As of September 30, 2019, the unrecognized stock-based compensation expense related to non-vested stock options and RSUs was $5,542 and $2,139, respectively, which will be amortized over an estimated weighted average period of approximately 2.31 and 2.59 years, respectively.

Note 5 — Stock-Based Compensation

We have a stock incentive plan for employees and others called the VirnetX Holding Corporation 2013 Equity Incentive Plan (the “Plan”), which has been approved by our stockholders. In April 2017, the Board approved an amendment and restatement of the Plan to, among other things, increase the shares reserved under the Plan by 2,500,000 shares (the “Plan Amendment”). Our stockholders approved of the Plan Amendment at the 2017 Annual Meeting of Stockholders held on June 1, 2017. The Plan provides for grants of 16,624,469 shares of our common stock, including stock options and restricted stock units (“RSUs”), and will expire in 2023. As of September 30, 2019, 1,128,903 shares remained available for grant under the Plan.

During the three months ended September 30, 2019, we did not grant any options. During the three months ended September 30, 2018, we granted options totaling 85,000 shares with a weighted average grant date fair value of $3.16.

During the nine months ended September 30, 2019, we granted options for a total of 345,000 shares. The weighted average fair value at the grant dates for options issued during the nine months ended September 30, 2019 was $4.63 per option. The fair values of options at the grant date were estimated utilizing the Black-Scholes valuation model with the following weighted average assumptions for the nine months ended September 30, 2019 (i) dividend yield on our common stock of 0 percent (ii) expected stock price volatility of 92 percent (iii) a risk-free interest rate of 2.09 percent and (iv) an expected option term of 6 years.

During the nine months ended September 30, 2018, we granted options for a total of 1,095,000 shares with a weighted average grant date fair value of $2.58. The fair values of options at the grant date were estimated utilizing the Black-Scholes valuation model with the following weighted average assumptions for the nine months ended September 30, 2018 (i) dividend yield on our common stock of 0 percent (ii) expected stock price volatility of 84 percent (iii) a risk-free interest rate average of 2.73 percent and (iv) an expected option term of 6 years.

During the three months ended September 30, 2019 and 2018, we did not grant any RSUs.

During the nine months ended September 30, 2019 and 2018, we granted 229,996 and 243,997 RSUs, respectively. The weighted average fair values at the grant dates for RSUs issued during the nine months ended September 30, 2019 and 2018 were $6.06 and $3.26 per RSU, respectively. RSUs, which are subject to forfeiture if service terminates prior to the shares vesting, are expensed ratably over the vesting period. During the nine months ended September 30, 2019 and 2018, we paid $47 and $42 in withholding taxes on shares issued upon conversion of RSUs. The underlying shares were canceled. These amounts are reflected as financing costs in the accompanying condensed consolidated statements of cash flows.

Stock-based compensation expense included in general and administrative expense was $565 and $1,437 and in research and development expense was $434 and $1,275 for the three and nine months ended September 30, 2019, respectively, and $592 and $1,447 for general and administrative expense and $425 and $1,580 for research and development expense for the three and nine months ended September 30, 2018, respectively.

As of September 30, 2019, the unrecognized stock-based compensation expense related to non-vested stock options and RSUs was $5,542 and $2,139, respectively, which will be amortized over an estimated weighted average period of approximately 2.31 and 2.59 years, respectively.