XML 18 R70.htm IDEA: XBRL DOCUMENT

Share-Based Compensation Plans Share-Based Compensation Plans - Black Scholes Option Price Model (Details) (Common Stock)	12 Months Ended
	Dec. 31, 2010
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.57%
Dividend yield	1.42%
Volatility factors of the expected market price for common stock	44.35%
Weighted average expected life of options	6 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