Note 12 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

	2017					2016					2015
	Shares			Weighted Average Fair Value		Shares			Weighted Average Fair Value		Shares			Weighted Average Fair Value
Nonvested at beginning of year		228,343		$	26.09		155,501		$	22.25		101,490		$	20.13
Granted		94,592			37.11		86,250			32.19		65,933			25.14
Vested		(74,979	)		20.17		(7,622	)		20.23		(4,666	)		20.13
Forfeited		(8,319	)		23.75		(5,786	)		21.90		(7,256	)		20.13
Nonvested at end of year		239,637		$	32.37		228,343		$	26.09		155,501		$	22.25

Share-based Compensation, Stock Options, Activity [Table Text Block]

	2017					2016					2015
	Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price
Outstanding at beginning of year		16,808		$	29.17		11,308		$	24.50		35,335		$	31.09
Granted		0			NA		6,500			36.22		4,820			27.66
Exercised		(1,000	)		22.15		(1,000	)		22.15		(2,700	)		6.21
Forfeited or expired		0			NA		0			NA		(26,147	)		35.88
Outstanding at end of year		15,808		$	29.62		16,808		$	29.17		11,308		$	24.50
Options exercisable at year-end		9,308		$	25.00		5,488		$	22.15		0		$	NA

	201 7					201 6					201 5
	Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price
Outstanding at beginning of year		44,275		$	9.86		123,887		$	12.64		217,982		$	14.89
Granted		0		NA			0		NA			0		NA
Exercised		(27,675	)		11.50		(71,711	)		13.33		(56,417	)		15.50
Forfeited or expired		(1,500	)		6.33		(7,901	)		22.00		(37,678	)		21.39
Outstanding at end of year		15,100		$	7.20		44,275		$	9.86		123,887		$	12.64
Options exercisable at year-end		15,100		$	7.20		44,275		$	9.86		123,887		$	12.64

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

	2016			2015
Risk-free interest rate		1.78	%		1.67	%
Expected option life (years)		5			5
Expected stock price volatility		26	%		29	%
Dividend yield		2.5	%		2.5	%

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

			Outstanding						Exercisable
					Weighted Average		Weighted				Weighted
Range of					Remaining		Average				Average
Exercise					Contractual		Exercise				Exercise
Prices			Number		Life (Years)		Price		Number		Price
$20.0 0	-	$24.00		4,488		3.9	$	22.15		4,488		22.15
$24.01	-	$28.00		4,820		4.9		27.66		4,820		27.66
$36.00	-	$40.00		6,500		5.9		36.22		0	NA
Outstanding at year end				15,808		5.0	$	29.62		9,308		25.00

			Outstanding						Exercisable
					Weighted Average		Weighted				Weighted
Range of					Remaining		Average				Average
Exercise					Contractual		Exercise				Exercise
Prices			Number		Life (Years)		Price		Number		Price
$4.00	-	$8.00		12,400		1.6	$	6.89		12,400	$	6.89
$ 8.01	-	$12.00		2,700		1.9		8.60		2,700		8.60
Outstanding at year end				15,100		1.7	$	7.20		15,100	$	7.20

Schedule of Share-based Compensation Shares Authorized Under Stock Option Plans Information Related to Option Outstanding [Table Text Block]

	201 7		201 6		201 5
Minimum exercise price	$	22.15	$	22.15	$	22.15
Maximum exercise price		36.22		36.22		27.66
Average remaining option term (y ears)		5.0		6.7		6.3

	201 7		201 6		201 5
Minimum exercise price	$	6.89	$	5.19	$	5.19
Maximum exercise price		8.60		16.00		22.00
Average remaining option term (years)		1.7		1.8		2.7

Schedule of Share Based Compensation Arrangement by Share Based Payment Award Options Information Related to Stock Option Grants and Exercised [Table Text Block]

	201 7		201 6		201 5
Aggregate intrinsic value of stock options exercised	$	15,000	$	6,000	$	36,000
Cash received from stock option exercises		0		22,000		17,000
Tax benefit realized from stock option exercises		0		0		0
Weighted average per share fair value of stock options granted		2.72		5.25		4.41

	201 7		201 6		201 5
Aggregate intrinsic value of stock options exercised	$	594,000	$	1,945,000	$	420,000
Cash received from stock option exercises		318,000		956,000		874,000
Tax benefit realized from stock option exercises		208,000		681,000		147,000
Weighted average per share fair value of stock options granted	NA		NA		NA