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Note 8 - Stock Compensation (Detail) - Fair Value Assumptions for Employee Stock Purchase Plan (Employe Stock Purchase Plan [Member])	3 Months Ended
	Mar. 31, 2013
Employe Stock Purchase Plan [Member]
Expected dividend yield at date of grant	0.00%
Expected stock price volatility	22.30%
Risk-free interest rate	0.14%
Expected term (in years)	1 year

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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