Stock-Based Compensation - Additional Information (Details) | 6 Months Ended |
Jun. 30, 2019USD ($)$ / sharesshares |
Restricted Stock Units (RSUs) | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition | 3 years 6 months 21 days |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period | 4 years |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value | $ 0.75 |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | $ | $ 400,000 |
Awarded, number of awards (in shares) | shares | 526,500 |
Fair value of RSUs awarded | $ | $ 400,000 |
2011 Equity Incentive Plan | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Intrinsic value of stock options exercisable | $ | 5,000 |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options | $ | $ 3,900,000 |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition | 2 years 9 months 3 days |
2011 Equity Incentive Plan | Certain Employees and Directors | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | shares | 2,557,042 |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period | 10 years |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Fair Value | $ | $ 1,300,000 |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate | 72.00% |
2011 Equity Incentive Plan | Certain Employees and Directors | Minimum | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price | $ 0.69 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value | $ 0.44 |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term | 5 years 6 months |
2011 Equity Incentive Plan | Certain Employees and Directors | Maximum | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price | $ 1 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value | $ 0.65 |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term | 6 years 29 days |
2011 Equity Incentive Plan | Employee Stock Option | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | shares | 2,557,000 |
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price | $ 0.77 |
2011 Equity Incentive Plan | Employee Stock Option | Certain Employees and Directors | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period | 4 years |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate | 0.00% |
2011 Equity Incentive Plan | Employee Stock Option | Certain Employees and Directors | Minimum | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate | 1.92% |
2011 Equity Incentive Plan | Employee Stock Option | Certain Employees and Directors | Maximum | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate | 2.63% |
2011 Equity Incentive Plan | Director Compensation Option | Director | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period | 1 year |
The 2015 Employee Stock Purchase Plan | |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | shares | 2,050,000 |