XML 21 R57.htm IDEA: XBRL DOCUMENT

Weighted Average Grant Date Fair Value of Option Shares Granted and Assumptions Used to Estimate those Values Using Black-Scholes Option Pricing Model (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Weighted average grant date fair value	$ 4.44	$ 5.10
Risk-free interest rate	1.09%	2.72%
Dividend yield	2.57%	2.34%
Volatility factor	50.97%	49.00%
Expected option life	6 years	6 years

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