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Share Based Compensation - Weighted Average Assumptions Used in Calculation of Fair Value for Service Condition Awards (Detail)
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12 Months Ended | ||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Market and performance condition awards [Member]
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| Share Based Payment Award Stock Options Valuation Assumptions [Line Items] | |||
| Expected volatility | 44.00% | ||
| Dividends yield | 1.40% | ||
| Expected term | 5 years 2 months 12 days | ||
| Risk-free interest rate | 1.20% | ||
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SARs [Member]
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| Share Based Payment Award Stock Options Valuation Assumptions [Line Items] | |||
| Expected volatility | 48.40% | 46.60% | 48.30% |
| Dividends yield | 2.70% | 1.50% | 1.80% |
| Expected term | 5 years 3 months 18 days | 6 years 2 months 12 days | 6 years 4 months 24 days |
| Risk-free interest rate | 0.70% | 1.90% | 2.40% |
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Incentive Plan and Independent Directors Stock Units [Member]
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| Share Based Payment Award Stock Options Valuation Assumptions [Line Items] | |||
| Expected volatility | 52.10% | 49.40% | 48.20% |
| Dividends yield | 2.70% | 1.50% | 1.70% |
| Expected term | 3 years 9 months 18 days | 3 years 9 months 18 days | 3 years 9 months 18 days |
| Risk-free interest rate | 0.40% | 1.00% | 1.30% |
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- Details
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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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- 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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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- 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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