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Share-Based Compensation - Weighted Average Assumptions Use in Calculation of Fair Value for Service, Performance Condition, and Market and Performance Condition Awards (Detail)
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12 Months Ended | ||
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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SARs [Member]
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| Share Based Payment Award Valuation Assumptions [Line Items] | |||
| Expected volatility | 50.80% | 48.40% | 46.60% |
| Dividends yield | 1.70% | 2.70% | 1.50% |
| Expected term | 5 years 6 months | 5 years 3 months 18 days | 6 years 2 months 12 days |
| Risk-free interest rate | 1.50% | 0.70% | 1.90% |
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Incentive Plan and Independent Directors Stock Units [Member]
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| Share Based Payment Award Valuation Assumptions [Line Items] | |||
| Expected volatility | 45.20% | 52.10% | 49.40% |
| Dividends yield | 1.50% | 2.70% | 1.50% |
| Expected term | 3 years 7 months 6 days | 3 years 9 months 18 days | 3 years 9 months 18 days |
| Risk-free interest rate | 0.70% | 0.40% | 1.00% |
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Performance condition awards [Member]
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| Share Based Payment Award Valuation Assumptions [Line Items] | |||
| Expected volatility | 50.90% | ||
| Dividends yield | 1.50% | ||
| Expected term | 5 years 6 months | ||
| Risk-free interest rate | 1.60% | ||
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Market and performance condition awards [Member]
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| Share Based Payment Award 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% | ||