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Stock-Based Compensation (Schedule Of Weighted Average Assumptions) (Details) (USD $)
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12 Months Ended | |||||
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2009
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||||
| Stock options granted | 340,973 | 385,924 | 387,505 | |||
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Stock Options [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||||
| Expected term, years | 5.12 | [1] | 4.53 | 4.71 | ||
| Expected stock price volatility | 30.76% | [1] | 28.79% | 29.52% | ||
| Risk-free interest rate | 1.84% | [1] | 1.91% | 1.73% | ||
| Expected dividend yield | 1.31% | [1] | 1.64% | 2.17% | ||
| Weighted average grant date fair value | 16.09 | [1] | 10.08 | 6.55 | ||
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Simplified Method [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||||
| Stock options granted | 53,720 | |||||
| Vesting period | fifth anniversary of the grant date | |||||
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| X | ||||||||||
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- Definition
Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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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- Details
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- Definition
Net number of share options (or share units) granted during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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