Stock Option Plans (Schedule Of Stock Options Valuation Assumptions) (Details)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock Option Plans [Line Items]
Expected dividends	0.00%
Employee Stock Purchase Plan [Member]
Stock Option Plans [Line Items]
Risk-free interest rate	0.20%	0.50%	1.20%
Expected lives in years	0.5	1.3	1.3
Expected dividends	0.00%	0.00%	0.00%
Expected volatility	36.00%	47.00%	50.00%
Stock Option Plans [Member]
Stock Option Plans [Line Items]
Risk-free interest rate	1.30%	1.60%	2.30%
Expected lives in years	5.6	5.7	5.5
Expected dividends	0.00%	0.00%	0.00%
Expected volatility	52.00%	54.00%	56.00%

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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