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Weighted-Average Assumptions Used in Monte Carlo Simulation (Details) (Restricted Stock Units, USD $)
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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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Restricted Stock Units
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| Schedule Of Restricted Stock [Line Items] | |||
| Expected volatility | 19.37% | 22.47% | 29.50% |
| Risk-free interest rate | 0.40% | 0.43% | 1.24% |
| Expected life (years) | 3 years | 3 years | 3 years |
| Grant date fair value per share | $ 40.13 | $ 37.40 | $ 29.95 |