Employee Stock-Based Compensation and Benefit Plans (Assumptions Used To Value Option Grants) (Details)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Expected dividend yield	0.00%	0.00%	0.00%
Minimum [Member]
Expected volatility factor	0.38%	0.31%	0.34%
Approximate risk free interest rate	0.60%	0.90%	1.20%
Expected term (in years)	3.27	3.06	3.17
Maximum [Member]
Expected volatility factor	0.50%	0.37%	0.44%
Approximate risk free interest rate	1.10%	1.60%	1.60%
Expected term (in years)	3.91	3.27	3.37

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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