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Employee Stock-Based Compensation and Benefit Plans (Assumptions Used To Value Option Grants) (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Market and Service Condition Stock Units [Member]
Approximate risk free interest rate	0.47%
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%
Employee Stock Option [Member]
Expected term (in years)	3 years 10 months 28 days
Expected dividend yield	0.00%	0.00%	0.00%
Employee Stock Option [Member] \| Minimum [Member]
Expected volatility factor	38.00%	38.00%	31.00%
Approximate risk free interest rate	0.50%	0.60%	0.90%
Expected term (in years)		3 years 3 months 7 days	3 years 0 months 22 days
Employee Stock Option [Member] \| Maximum [Member]
Expected volatility factor	43.00%	50.00%	37.00%
Approximate risk free interest rate	0.70%	1.10%	1.60%
Expected term (in years)		3 years 10 months 28 days	3 years 3 months 7 days

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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