Note 3 - Stock-based Compensation and Shareholders' Equity (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Assumptions Used in Option Pricing Model

Nine months ended September 30,	2018			2017
Risk free interest rate		2.15	%		1.48	%
Dividend yield		1.24	%		3.19	%
Volatility		18.12	%		17.89	%
Expected life (years)		4.20			4.20

Stock Option Activity

	Number of options			Weighted average exercise price		Weighted average remaining contractual term (in years)		Aggregate intrinsic value
Outstanding at December 31, 2017		85,525		$	30.94
Granted		25,000			43.60
Exercised		(10,000	)		24.86
Forfeited		(1,600	)		32.52
Outstanding at September 30, 2018		98,925		$	34.73		2.74	$	1,105
Exercisable at September 30, 2018		26,525		$	27.46		0.90	$	489

	Number of options			Weighted average exercise price		Weighted average remaining contractual term (in years)		Aggregate intrinsic value
Outstanding at December 31, 2016		73,950		$	27.14
Granted		25,000			37.60
Exercised		(11,775	)		22.33
Forfeited		(100	)		21.35
Outstanding at September 30, 2017		87,075		$	30.80		2.87	$	848
Exercisable at September 30, 2017		20,725		$	24.39		0.93	$	335