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Share-Based Compensation (Details)
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12 Months Ended | ||
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Dec. 31, 2011
Y
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Dec. 31, 2010
Y
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Dec. 31, 2009
Y
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SARS [Member]
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| Weighted average assumptions used in the calculation of the fair value for service condition awards | |||
| Expected volatility | 46.60% | 48.30% | 48.50% |
| Dividends yield | 1.50% | 1.80% | 5.70% |
| Expected term | 6.2 | 6.4 | 6.5 |
| Risk-free interest rate | 1.90% | 2.40% | 2.30% |
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Independent Director's SARS [Member]
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| Weighted average assumptions used in the calculation of the fair value for service condition awards | |||
| Expected volatility | 49.40% | 48.20% | 48.60% |
| Dividends yield | 1.50% | 1.70% | 5.80% |
| Expected term | 3.8 | 3.8 | 3.8 |
| Risk-free interest rate | 1.00% | 1.30% | 1.40% |
| X | ||||||||||
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- Details
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| X | ||||||||||
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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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The estimated measure of the 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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