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Stock-Based Compensation (Weighted-Average Assumptions Used To Value The Options Granted) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Stock-Based Compensation [Abstract]
Expected term of options	6 years	5 years	6 years 8 months 12 days	6 years 2 months 12 days
Expected volatility	43.00%	42.00%	42.00%	41.00%
Risk-free interest rate	1.047%	1.877%	1.306%	2.674%
Dividend yield	0.00%	0.00%	0.00%	0.00%

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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