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Employee Benefit Plans (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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| Weighted-average assumptions for calculating fair values of stock options granted | |||
| Contractual life (in years) | 4.2 | ||
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Stock options granted [Member]
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| Weighted-average assumptions for calculating fair values of stock options granted | |||
| Expected volatility | 27.30% | 28.60% | 28.70% |
| Risk-free interest rate | 1.70% | 2.40% | 1.40% |
| Dividend yield | 2.70% | 2.90% | 3.10% |
| Expected life (in years) | 4.4 | 4.3 | 4.2 |
| Contractual life (in years) | 7 | 7 | 7 |
| 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 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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| X | ||||||||||
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- Definition
The range of expected volatilities used and the weighted-average expected volatility for an entity using a valuation technique with different volatilities during the contractual term. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The weighted average period between the balance sheet date and expiration for all awards outstanding under the plan, which may be expressed in a decimal value for number of years. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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