Stockholders' Equity (Schedule Of Black-Scholes Assumptions Used For Stock Options) (Details) (Stock Option [Member], USD $)	3 Months Ended
Mar. 31, 2012 Y	Mar. 31, 2011 Y
Stock Option [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Risk-free interest rate, minimum	0.99%	2.33%
Risk-free interest rate, maximum	1.01%	2.34%
Estimated term (in years)	5.48	5.99
Estimated volatility	73.00%	81.00%
Estimated dividend yield	0.00%	0.00%
Weighted-average grant-date fair value per share of options granted	$ 35.78	$ 11.07

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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