Stock-Based Compensation (Summary Of Share Based Payment Other Than Options Valuation Assumptions) (Detail)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected volatility of stock price	43.00%	49.00%

- Definition

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.

+ References+ Details