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Note 2 - Stock-Based Compensation (Detail) - 2004 Employee Stock Purchase Plan Fair Value Assumptions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Dividend yield	0.00%
Two Thousand Four Employee Stock Purchase Plan [Member]
Expected term (years)	6 months	6 months
Expected volatility	28.50%	50.70%
Risk-free interest rate	0.10%	0.10%
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.

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