XML 32 R43.htm IDEA: XBRL DOCUMENT

Stock-Based Compensation (Weighted-Average Assumptions Used to Determine Fair Value of Options Granted) (Detail)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected dividend yield	0.00%	0.00%
Risk-free interest rate	0.57%	0.69%
Expected life (years)	3 years 8 months	3 years 9 months
Volatility	48.00%	58.00%

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