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Stock-based compensation Stock-based compensation (Details 1) (Stock Options [Member], USD $)
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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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Stock Options [Member]
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| Weighted-average assumptions and resulting weighted-average grant date fair values [Abstract] | |||
| Closing price of our common stock on grant date | $ 74.56 | $ 54.66 | $ 58.32 |
| Expected volatility | 22.20% | 23.50% | 28.00% |
| Expected life (in years) | 8 years 1 month 6 days | 5 years 10 months 24 days | 6 years 7 months 6 days |
| Risk-free interest rate | 1.60% | 2.50% | 3.20% |
| Expected dividend yield | 2.10% | 2.00% | 0.00% |
| Fair value of stock options granted | $ 14.65 | $ 11.39 | $ 20.97 |
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- Definition
The closing price of our common stock on grant date used to estimate the grant date fair value of our stock-based compensation. No definition available.
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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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- 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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