| **Share-based Compensation - Principal Assumptions Utilized in Valuing SSARs Granted (Details) (Stock Settled Stock Appreciation Rights [Member], USD $)** | 12 Months Ended |
|------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------|
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| Stock Settled Stock Appreciation Rights [Member]                                                                                                           |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]**                                   |            |   |   |
| Risk-free interest rate, minimum                                                                                                                           | 1.05%           | 0.67% | 0.83% |
| Risk-free interest rate, maximum                                                                                                                           | 1.39%           | 0.89% | 2.09% |
| Expected life (in years)                                                                                                                                   | 5 years         | 5 years | 4 years 6 months |
| Expected volatility, minimum                                                                                                                               | 80.78%          | 81.03% | 80.75% |
| Expected volatility, maximum                                                                                                                               | 80.93%          | 83.77% | 82.20% |
| Weighted average grant date fair value (in dollars per share)                                                                                              | $ 4.92          | $ 4.73 | $ 7.96 |

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| - Definition
The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.
+ 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)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| - Definition
Expected term of share-based compensation awards, 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 S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.D.2) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section D -Subsection 2
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| - Definition
The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| - Definition
The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.
+ References
No definition available.
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| - Definition
The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                  |
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| - Definition
The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.
+ References
No definition available.
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