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Stock-Based Compensation - Additional Information (Details) |  |  |  |  | 1 Months Ended | 12 Months Ended |  |
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Jan. 01, 2018 shares | Aug. 31, 2016 USD ($) shares | Aug. 23, 2016 USD ($) $ / shares shares | Feb. 29, 2016 USD ($) shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 shares | May 31, 2015 shares | Jun. 30, 2014 shares | Jun. 30, 2010 USD ($) Period shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) shares | Dec. 31, 2015 shares | Dec. 31, 2014 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of replacement options |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |
Options expired in relation to the offer |  |  | 456,995 |  |  |  |  |  |  |  |  |  |  |
Options granted (in shares) |  |  | 334,027 |  |  |  |  |  |  |  |  |  |  |
Shares eligible for purchase via options |  |  | 113,531 |  |  |  |  |  |  |  |  |  |  |
Exercise price of replacement options | $ / shares |  |  | $ 7.20 |  |  |  |  |  |  |  |  |  |  |
Incremental charge resulting from the plan modification | $ |  |  | $ 926,000 |  |  |  |  |  |  |  |  |  |  |
Amortization period of incremental charge |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |
New Employees |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding awards |  |  |  |  | 0 | 0 |  |  |  | 0 | 0 |  |  |
Options |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unamortized compensation cost, net of expected forfeitures | $ |  |  |  |  | $ 300,000 |  |  |  |  | $ 300,000 |  |  |  |
Weighted average expected period over which the expense is to be recognized |  |  |  |  |  |  |  |  |  | 9 months 18 days |  |  |  |
Fair value of vested options and awards | $ |  |  |  |  |  |  |  |  |  | $ 700,000 |  |  |  |
Tax benefits associated with exercise of stock options | $ |  |  |  |  |  |  |  |  |  | $ 0 | $ 0 | $ 0 |  |
Dividend yield (as a percent) |  |  |  |  |  |  |  |  |  | 0.00% | 0.00% | 0.00% |  |
Stock options exercised |  |  |  |  |  |  |  |  |  | 0 | 0 | 0 |  |
Employee stock purchase plan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares authorized and unissued |  |  |  |  | 150,000 |  |  |  |  | 150,000 |  |  |  |
Number of shares reserved for issuance |  |  |  |  |  |  |  |  | 200,000 |  |  |  |  |
Increase in number of shares reserved for issuance |  |  |  |  |  |  | 200,000 |  |  |  |  |  |  |
Number of offering periods | Period |  |  |  |  |  |  |  |  | 2 |  |  |  |  |
Offering period |  |  |  |  |  |  |  |  | 6 months |  |  |  |  |
Purchase price to be paid by participants as a percentage of price per share either at the beginning or the end of each six-month offering period, whichever is less |  |  |  |  |  |  |  |  | 85.00% |  |  |  |  |
Shares of common stock issued under the plan |  | 31,900 |  | 37,300 |  |  |  |  |  |  |  |  |  |
Aggregate purchase price of shares issued | $ |  | $ 167,000 |  | $ 197,000 |  |  |  |  |  |  |  |  |  |
Employee stock purchase plan | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum amount of shares that eligible employee may purchase annually (in dollars) | $ |  |  |  |  |  |  |  |  | $ 25,000 |  |  |  |  |
RSU's |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unamortized compensation cost, net of expected forfeitures | $ |  |  |  |  | $ 100,000 |  |  |  |  | $ 100,000 |  |  |  |
Weighted average expected period over which the expense is to be recognized |  |  |  |  |  |  |  |  |  | 3 months 18 days |  |  |  |
Amended 2000 Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares authorized and unissued |  |  |  |  | 0 |  |  |  |  | 0 |  |  |  |
Equity Incentive Plan 2010 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares authorized and unissued |  |  |  |  | 4,007,000 | 231,000 |  |  |  | 4,007,000 | 231,000 | 114,000 | 106,000 |
Number of shares reserved for issuance |  |  |  |  |  |  |  |  |  |  |  |  |  | 400,000
Increase in number of shares reserved for issuance | 50,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Term of Plan |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |
Options expired in relation to the offer |  |  |  |  |  |  |  |  |  |  |  | 58,000 |  |
Options granted (in shares) |  |  |  |  |  |  |  |  |  | 40,000 | 160,000 | 384,000 |  |
Equity Incentive Plan 2010 | Options |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in number of shares reserved for issuance |  |  |  |  | 4,000,000 | 200,000 |  | 150,000 |  | 4,050,000 | 250,000 | 50,000 |  |
Maximum annual option grants or other awards to the entity's non-employee directors (in shares) |  |  |  |  | 40,000 |  |  |  |  | 40,000 |  |  |  |
Maximum one-time grant of an option or other awards to the entitiy's non employee directors (in shares) | $ |  |  |  |  |  |  |  |  |  | $ 120,000 |  |  |  |
Maximum term of options granted |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |
Minimum percentage of voting rights required for applicability of a specific expriation term |  |  |  |  | 10.00% |  |  |  |  | 10.00% |  |  |  |
Maximum expiration term of options granted |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |
Vesting period of replacement options |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |
Equity Incentive Plan 2010 | Options | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of Plan |  |  |  |  |  |  |  |  |  | 6 years |  |  |  |
Equity Incentive Plan 2010 | Options | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of Plan |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |
Equity Incentive Plan 2010 | RSU's |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total intrinsic value of the RSUs outstanding | $ |  |  |  |  | $ 100,000 |  |  |  |  | $ 100,000 |  |  |  |

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- Definition Represents the shares reserved for one-time grant under option or other awards to the entity's non-employee directors under the share-based compensation plan. + References No definition available. + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + 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 (i) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + 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)(iii) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + 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 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements. + 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 (c)(1)(iv)(4) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition An excess of the fair value of the modified award over the fair value of the award immediately before the modification. + 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)(2)(iii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Number of share instruments newly issued under a share-based compensation plan. + 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 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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