Stock-Based Compensation (Assumptions Used To Value Option Grants) (Details)	3 Months Ended
Mar. 31, 2012 Y	Mar. 31, 2011 Y
Expected volatility factor	38.00%	39.00%
Approximate risk free interest rate	0.65%	1.10%
Expected term (in years)	3.91	3.27
Expected dividend yield	0.00%	0.00%
Market and Service Condition Stock Units [Member]
Approximate risk free interest rate	0.47%
Expected term (in years)	2.75
Expected dividend yield	0.00%
Market and Service Condition Stock Units [Member] \| Minimum [Member]
Expected volatility factor		21.00%
Market and Service Condition Stock Units [Member] \| Maximum [Member]
Expected volatility factor		39.00%

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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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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