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

3 Months Ended

Mar. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Assumptions Used in Option Pricing Model

Three months ended March 31,	2017			2016
Risk free interest rate		1.48	%		1.14	%
Dividend yield		3.19	%		3.78	%
Volatility		17.89	%		22.62	%
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, 2016		73,950		$	27.14
Granted		25,000			37.60
Exercised		(10,375	)		22.21
Forfeited		(100	)		21.35
Outstanding at March 31, 2017		88,475		$	30.68		3.33	$	661
Exercisable at March 31, 2017		22,125		$	24.31		1.39	$	306

	Number of options			Weighted average exercise price		Weighted average remaining contractual term (in years)		Aggregate intrinsic value
Outstanding at December 31, 2015		82,875		$	24.33
Granted		23,500			30.40
Exercised		(17,900	)		20.65
Forfeited		(9,225	)		25.77
Outstanding at March 31, 2016		79,250		$	26.79		3.22	$	264
Exercisable at March 31, 2016		24,125		$	22.38		1.37	$	184