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Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands |  |  | 1 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Jun. 16, 2016 | Dec. 03, 2014 | Oct. 31, 2014 | Jul. 31, 2012 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Unrecognized compensation cost related to outstanding options |  |  |  |  |  | $ 2,600 | $ 3,900 |
Intrinsic value of options exercised |  |  |  |  |  | $ 10 | 300 |
Weighted average grant date fair value of vested options |  |  |  |  |  | $ 4.71 |  |
Weighted average grant date fair value of options outstanding |  |  |  |  |  | $ 3.67 |  |
Stock-based compensation expense |  |  |  |  |  | $ 1,548 | 1,228 |
2012 Equity Incentive Plan [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Number of shares authorized for issuance |  |  |  |  |  |  |  | 609,389
Stock options vesting period |  |  |  | 3 years |  |  |  |
Term of stock options granted |  |  |  | 10 years |  |  |  |
2012 Equity Incentive Plan [Member] | First Anniversary of Original Vesting Date [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Stock options vesting percentage |  |  |  | 25.00% |  |  |  |
2013 Equity Incentive Plan [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Stock options vesting period |  |  | 3 years |  |  |  |  |
Term of stock options granted |  |  | 10 years |  |  |  |  |
2013 Equity Incentive Plan [Member] | First Anniversary of Original Vesting Date [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Stock options vesting percentage |  |  | 25.00% |  |  |  |  |
2013 Equity Incentive Plan [Member] | EIP Amendment [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Increase in authorized shares of common stock amount | 300,000 |  |  |  |  |  |  |
Increase in authorized shares, percentage of common stock outstanding |  |  | 4.00% |  |  |  |  |
2013 Employee Stock Purchase Plan [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Number of shares authorized for issuance |  | 103,665 |  |  |  |  |  |
Increase in authorized shares of common stock amount |  | 51,832 |  |  |  |  |  |
Increase in authorized shares, percentage of common stock outstanding |  | 1.00% |  |  |  |  |  |
General and Administrative [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Stock-based compensation expense |  |  |  |  |  | 1,057 | 777 |
Restricted stock-based compensation expense |  |  |  |  |  | $ 2 | $ 4 |
Scenario, Forecast [Member] | 2013 Equity Incentive Plan [Member] | EIP Amendment [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Increase in authorized shares of common stock amount |  |  |  |  | 825,904 |  |  |
Scenario, Forecast [Member] | 2013 Employee Stock Purchase Plan [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Increase in authorized shares of common stock amount |  |  |  |  | 206,476 |  |  |
Stock Options [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Unrecognized compensation cost, recognition period |  |  |  |  |  | 2 years 4 days | 2 years 8 months 5 days |
Restricted Stock [Member] |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Unrecognized compensation cost, recognition period |  |  |  |  |  | 3 months 18 days | 1 year 2 months 12 days |
Unrecognized compensation cost related to restricted stock awards |  |  |  |  |  | $ 1 | $ 4 |

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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -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=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of additional shares authorized for issuance under an established share-based compensation plan. + References No definition available. + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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