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

3 Months Ended

Mar. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Assumptions Used in Option Pricing Model

Three months ended March 31,	2019			2018
Risk free interest rate		2.52	%		2.15	%
Dividend yield		3.36	%		1.24	%
Volatility		16.44	%		18.12	%
Expected life (years)		4.17			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, 2018		95,075		$	35.11
Granted		24,700			38.15
Exercised		(8,275	)		25.38
Forfeited		—			—
Outstanding at March 31, 2019		111,500		$	36.51		3.08	$	270
Exercisable at March 31, 2019		37,350		$	29.96		1.48	$	270

	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		(9,750	)		24.75
Forfeited		—			—
Outstanding at March 31, 2018		100,775		$	34.68		3.23	$	944
Exercisable at March 31, 2018		27,275		$	27.51		1.41	$	451