Note 1 - Nature of Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	2014		2013		2012
Dividend yield		.47%		.44% to .53%		.86%
Expected volatility		29.07% to 29.18%		29.50% to 30.56%		29.36%
Risk-free interest rate		2.69% to 2.82%		1.71% to 2.90%		1.98%
Expected life of option grants (years)		6		6		6
Weighted-average grant date fair value	$	5.68	$	5.14	$	2.79

	2014		2013		2012
Dividend yield		.46% to .47%		.53% to .61%		.61% to .88%
Expected volatility		16.96% to 19.35%		23.05% to 24.25%		27.20% to 31.11%
Risk-free interest rate		.04% to .12%		.10% to .18%		.03% to .18%
Expected life of purchase grants (months)		3 to 6		3 to 6		3 to 6
Weighted-average grant date fair value	$	2.37	$	2.10	$	1.71