XML 16 R70.htm IDEA: XBRL DOCUMENT

Stock-Based Compensation (Details 8)	12 Months Ended
Stock-Based Compensation (Details 8)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Options [Member]
Schedule of stock option and employee stock purchase plan, valuation assumptions
Expected life (in years)	4 years 6 months	4 years 6 months	5 years 2 months 12 days
Interest rate	0.70%	0.80%	1.40%
Volatility	70.00%	72.00%	68.00%
Dividend yield	0.00%	0.00%	0.00%
Employee Stock [Member]
Schedule of stock option and employee stock purchase plan, valuation assumptions
Expected life (in years)	6 months	6 months	6 months
Interest rate	0.10%	0.20%	0.60%
Volatility	62.00%	45.00%	80.00%
Dividend yield	0.00%	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