XML 57 R111.htm IDEA: XBRL DOCUMENT

Summary Of Share Based Payment Other Than Options Valuation Assumptions (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility of stock price	50.00%	48.00%	54.00%
Risk-free interest rate - minimum	0.30%	0.47%
Risk-free interest rate - maximum	0.42%	1.21%
Valuation period, minimum (in years)	2.5 years	3 years
Valuation period, maximum (in years)	3 years	4 years
Dividend yield	0.00%	0.00%	0.00%

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