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Share-Based Compensation - Stock Options Unvested (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Unvested Stock Options |  |  |
Unvested stock options |  |  |
Options outstanding at the beginning of the period (in shares) | 57,000 |  |
Granted (in shares) | 124,000 |  |
Vested (in shares) | (147,000) |  |
Options outstanding at the end of the period (in shares) | 34,000 | 57,000 |
Weighted-Average Grant-Date Fair Value |  |  |
Options outstanding at the beginning of the period (in dollars per share) | $ 5.34 |  |
Granted (in dollars per share) | 2.86 |  |
Vested (in dollars per share) | 3.27 |  |
Options outstanding at the end of the period (in dollars per share) | $ 5.21 | $ 5.34 |
Total future compensation cost related to unvested options that are expected to vest | $ 0.1 |  |
Weighted Average Period for Cost recognition | 1 year |  |
Key Officer Director and Managerial Employee Stock Options |  |  |
Unvested stock options |  |  |
Granted (in shares) | 124,000 | 99,711 |
Weighted-Average Grant-Date Fair Value |  |  |
Granted (in dollars per share) | $ 2.86 | $ 3.52 | $ 4.40
Total intrinsic value of stock options exercised | $ 5.1 | $ 0.3 | $ 0.8
Total fair value of option vested during the period | $ 0.5 | $ 1.9 | $ 1.9

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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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- Definition Unrecognized cost of unvested options awarded to employees as compensation. + 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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- 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Net number of share options (or share units) granted during the period. + 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 (c)(1)(iv)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + 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 (d)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of non-vested options outstanding. + References No definition available. + Details
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- Definition Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock. + 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 (c) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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