XML 15 R48.htm IDEA: XBRL DOCUMENT

Share-Based Employee Compensation Plans and Other Compensation and Benefit Plans (Black-Scholes Option Pricing Model) (Details) (Stock Option [Member])	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Stock Option [Member]
Risk-free interest rate	0.67%	1.63%
Expected life	4 years 1 month	4 years 1 month 7 days
Expected volatility	33.70%	33.40%
Expected dividend yield	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