Note 11 - Stock Options Valuation Assumptions (Details) - $ / shares		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Expected option life in years(1) (Year)	[1]	6 years	6 years	6 years
Expected stock price volatility percentage(2)	[2]	25.00%	25.00%	27.00%
Risk-free interest rate percentage(3)	[3]	1.40%	1.80%	1.90%
Expected dividend yield(4)	[4]	0.50%	0.44%	0.46%
Fair value as of the date of grant (in dollars per share)		$ 5.28	$ 5.96	$ 6.25

[1] We use historical employee exercise and option expiration data to estimate the expected life assumption for the Black-Scholes grant-date valuation. We believe that this historical data is currently the best estimate of the expected term of a new option. We use a weighted-average expected life for all awards.

[2] We use our stock's historical volatility for the same period of time as the expected life. We have no reason to believe that its future volatility will differ from the past.

[3] The rate is based on the U.S. Treasury yield curve in effect at the time of the grant for the same period of time as the expected life.

[4] The calculation is based on the total expected annual dividend payout divided by the average stock price.