XML 16 R37.htm IDEA: XBRL DOCUMENT

Stockholders' Equity (Summary Of Assumptions Used To Value Stock Option Grants Using Lattice-Binomial Model) (Details)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Stockholders' Equity Note [Abstract]
Dividend yield	0.00%	0.00%
Expected volatility	54.00%	65.00%
Risk-free interest rate	1.87%	1.97%
Suboptimal exercise factor, minimum	2.33	2.26
Suboptimal exercise factor, maximum	3.59	3.65

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