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Stock-Based Compensation (Schedule of ESPP Granted Black Scholes) (Details) (1999 ESPP [Member])	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
1999 ESPP [Member]
Expected life (years)	6 months	6 months	6 months
Risk free interest rate (%)	0.10%	0.10%	0.20%
Expected volatility (%)	51.00%	43.70%	51.20%
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.

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