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Share-Based Compensation (Narrative) (Details) $ in Thousands |  |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Feb. 28, 2017 USD ($) | Jan. 01, 2008 | Feb. 28, 2018 executive | Mar. 31, 2017 USD ($) shares | Feb. 29, 2016 shares | Mar. 31, 2017 USD ($) | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) shares | Dec. 31, 2015 shares | Feb. 28, 2015 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of executives | executive |  |  | 4 |  |  |  |  |  |  |  |
Vesting term |  |  |  |  |  |  | 4 years |  |  |  |
Intrinsic value of stock options exercised | $ |  |  |  |  |  | $ 371 | $ 42 |  | $ 591 |  |
Total fair value of stock options vested | $ |  |  |  |  |  |  | $ 0 | $ 142 | $ 142 |  |
Target restricted stock granted during period |  |  |  |  |  |  | 20,500 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Performance Period |  |  |  |  |  |  | 3 years |  |  |  |
Restricted Stock And Restricted Stock Unit [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
RSU available for issuance (in share) |  |  |  |  |  |  | 75,250 | 169,000 | 271,000 | 263,250 |
Granted, shares (in shares) |  |  |  |  |  |  | 0 | 0 | 95,750 |  |
RSUs vested during period (in shares) |  |  |  |  |  |  | 0 | 82,000 | 78,500 |  |
Restricted Stock [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Equity instruments other than options, vested in period, fair value | $ |  |  |  | $ 3,600 |  |  |  |  |  |  |
RSUs vested during period (in shares) |  |  |  | 61,444.90 | 146,896 |  |  |  |  |  |
2015 Plan [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of shares authorized (in shares) |  |  |  |  |  |  |  |  |  |  | 4,900,000
Options granted during period |  |  |  |  |  |  |  | 0 | 0 |  |
Compensation expense not yet recognized | $ |  |  |  |  |  |  | $ 500 |  |  |  |
Compensation expense not yet recognized, period for recognition |  |  |  |  |  |  | 3 years 1 month 9 days |  |  |  |
2015 Plan [Member] | Employee Stock Option [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of options available for issuance (in shares) |  |  |  |  |  |  | 80,000 |  |  |  |
2015 Plan [Member] | Restricted Stock [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
RSU available for issuance (in share) |  |  |  |  |  |  | 75,250 |  |  |  |
2005 Plan [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Percentage of stock option exercisable per year |  |  |  |  |  |  | 25.00% |  |  |  |
Stock option expiration period (in years) |  | 10 years |  |  |  |  |  |  |  |  |
Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Shares issued during period |  |  |  |  | 88,074 |  |  |  |  |  |
Shares withheld for payroll taxes |  |  |  |  | 58,822 |  |  |  |  |  |
Common Stock [Member] | 2015 Plan [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of shares available for issuance (in shares) |  |  |  |  |  |  | 4,744,750 |  |  |  |
Additional Paid-in Capital [Member] |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Reclassification of restricted stock units from equity to liability award | $ | $ 200 |  |  |  |  |  | $ 0 | $ 0 | $ 3,435 |  |

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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target 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 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + 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)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + 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 Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer. + References No definition available. + Details
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