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Stock-Based Compensation (Details Textual) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Other information |  |  |
Allocated Share-based Compensation Expense | $ 4.4 | $ 4.7 | $ 4.8
Stock Option [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercisable period from date of grant | 10 years |  |
Long-Term Incentive Plan [Member] |  |  |
Other information |  |  |
Total unrecognized stock-based compensation expense | $ 4.4 |  |
Long-Term Incentive Plan [Member] | Maximum [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Maximum Grants Of Awards (in shares) | 900,000 |  |
Restricted Awards [Member] |  |  |
Other information |  |  |
Total unrecognized stock-based compensation expense | $ 2.5 |  |
Weighted average vesting period | 1 year 4 months 24 days |  |
Performance awards [Member] |  |  |
Other information |  |  |
Total unrecognized stock-based compensation expense | $ 1.9 |  |
Weighted average vesting period | 1 year 9 months 18 days |  |
Performance awards [Member] | Maximum [Member] |  |  |
Weighted-Average Grant Date Fair Value |  |  |
Potential Payout As a Percentage of Target Shares | 200.00% |  |
Internal metric-based performance awards [Member] |  |  |
Other information |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period | 2 years 9 months 18 days |  |

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- Definition The percentage of target shares, an employee can earn, under the plan. + References No definition available. + Details
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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=96867065&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=96867065&loc=d3e5070-113901 + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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