XML 62 R41.htm IDEA: XBRL DOCUMENT

Stock-based Compensation - Weighted-Average Assumptions (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected life in years	6 years 3 months 18 days	6 years 2 months 12 days
Risk-free interest rate	1.36%	1.37%
Volatility	54.00%	57.00%
Dividend yield
Weighted-average fair value of stock options granted	$ 3.38	$ 5.98

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