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Stockholders' Equity - Narrative (Details) |  |  | 1 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 16, 2015 USD ($) | Sep. 11, 2015 $ / shares shares | Sep. 30, 2013 shares | Dec. 31, 2018 USD ($) plan $ / shares shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 shares | Dec. 31, 2015 | Jun. 21, 2017 shares | Jul. 22, 2015 shares | May 06, 2014 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Issuance of common stock (in shares) |  | 1,500,000 |  |  |  |  |  |  |  |
Share price (in dollars per share) | $ / shares |  | $ 17.00 |  | $ 0.62 |  |  |  |  |  |
Proceeds from issuances of common stock, net | $ | $ 23,600,000 |  |  |  |  |  |  |  |  |
Number of additional other equity-based plans | plan |  |  |  | 2 |  |  |  |  |  |
Vesting period |  |  |  | 10 years |  |  |  |  |  |
Unamortized stock compensation expense | $ |  |  |  | $ 900,000 | $ 700,000 |  |  |  |  |
Remaining weighted average life |  |  |  | 1 year 9 months 15 days | 1 year 9 months 15 days |  |  |  |  |
Exercised (in shares) |  |  |  | 0 | 42,000 | 79,166 |  |  |  |
Intrinsic value of options outstanding | $ |  |  |  | $ 0 |  |  |  |  |  |
Intrinsic value of options exercisable | $ |  |  |  |  | $ 0.00 |  |  |  |  |
2013 Plan |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of shares authorized (in shares) |  |  | 500,000 |  |  |  |  |  |  |
Number of shares available for grant (in shares) |  |  |  | 401,484 |  |  |  |  |  |
Purchase price of common stock, percent |  |  | 85.00% |  |  |  |  |  |  |
Shares issued in the period (in shares) |  |  |  | 25,953.000 | 16,004.000 | 22,094 |  |  |  |
Restricted stock |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting period |  |  |  | 1 year |  |  |  |  |  |
Minimum | Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting periods |  |  |  |  |  |  | 1 year |  |  |
Minimum | Employee stock option |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting period |  |  |  | 1 year |  |  |  |  |  |
Maximum | Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting periods |  |  |  |  |  |  | 3 years |  |  |
Maximum | Employee stock option |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting period |  |  |  | 4 years |  |  |  |  |  |
2014 Plan |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of shares authorized (in shares) |  |  |  |  |  |  |  | 1,300,000 | 600,000 | 600,000
Number of shares available for grant (in shares) |  |  |  | 1,269,815 |  |  |  |  |  |
Vesting periods |  |  |  | 10 years |  |  |  |  |  |
2014 Plan | Minimum |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting period |  |  |  | 3 years |  |  |  |  |  |
2014 Plan | Maximum |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting period |  |  |  | 4 years |  |  |  |  |  |
Shares sold by selling stockholders |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Issuance of common stock (in shares) |  | 1,500,000 |  |  |  |  |  |  |  |

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