Stock Option Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock Option Activity

	2017			2016
Options outstanding  at the
beginning of the year		1,088,278			1,267,802
Options granted		313,900			171,000
Options forfeited		(4,000	)		(33,825	)
Options exercised		(109,098	)		(316,699	)
Options outstanding at
the end of the year		1,289,080			1,088,278
Options exercisable at the
end of the year		814,180			769,403
Common stock available for future grants at the end of the year		62,700			66,850
Weighted average exercise price per share:
Granted	$	24.87		$	21.41
Forfeited		19.12			15.03
Exercised		13.13			10.99
Outstanding		16.87			14.18
Exercisable		13.38			12.29

Summary of Options Outstanding

	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number Outstanding	Weighted-Average Remaining Contractual Life (Years)		Weighted- Average Exercise Price	Number Exercisable		Weighted- Average Exercise Price
$7.30 to $10.38	234,180	3	$	9.57	234,180	$	9.57
$10.39 to $13.68	218,250	4		11.40	218,250		11.40
$13.69 to $16.98	308,250	6		15.44	268,000		15.26
$16.99 to $24.43	313,500	9		21.91	72,750		20.36
$24.44 to $28.20	214,900	9		25.31	21,000		28.16
	1,289,080				814,180

Assumptions Used to Value Option Grants

	2017		2016
Expected life in years		5		5
Interest rate		1.82 – 1.95%		1.07 – 1.24%
Volatility		.259-.277		.236-.258
Dividend yield		1.5% - 1.6%		1.6% - 2.0%