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Note 4 - Share-Based Compensation (Detail) - Stock Options Valuation Assumptions	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Minimum [Member]
Expected dividend yield at date of grant	2.63%	2.00%
Expected stock price volatility	29.10%	26.70%
Risk-free interest rate	0.56%	1.70%
Expected life of options (in years)	4 years	4 years
Maximum [Member]
Expected dividend yield at date of grant	3.98%	2.55%
Expected stock price volatility	31.70%	32.00%
Risk-free interest rate	1.15%	2.14%
Expected life of options (in years)	6 years	6 years

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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