XML 105 R69.htm IDEA: XBRL DOCUMENT

Stock-Based Compensation Expense - Weighted-Average Assumptions Used in Estimating Fair Values of Stock Options Granted (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Stock Options [Line Items]
Risk-free rate	2.00%	2.90%	3.30%
Expected dividend yield	1.20%	1.10%	1.30%
Expected volatility	44.00%	43.00%	44.00%
Expected term (in years)	5 years 8 months 12 days	5 years 6 months	5 years 3 months 18 days

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