Stock Based Compensation Plans (Details 2) (USD $)	12 Months Ended
Dec. 31, 2011 Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y
Weighted average grant date fair value of these SARs
Weighted average exercise price per share	$ 51.17	$ 46.09	$ 36.90
Expected annual dividends per share	0.31%	0.35%	0.44%
Expected life in years	3.7	3.6	3.5
Expected volatility	47.00%	49.00%	58.00%
Risk-free interest rate	1.40%	1.60%	1.50%
Weighted average grant date fair value	$ 18.22	$ 17.01	$ 15.42

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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.

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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.

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