Note 15 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

	2016		2015		2014
Stock option and incentive plans	$	885,757	$	885,524	$	832,845
Stock purchase plan		61,417		55,945		58,774
	$	947,174	$	941,469	$	891,619

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

	December 31,
	2016					2015					2014
				Weighted					Weighted					Weighted
				Average					Average					Average
				Exercise					Exercise					Exercise
	Shares			Price		Shares			Price		Shares			Price
Outstanding, beginning		623,176		$	13.88		661,771		$	13.89		662,506		$	13.82
Granted		76,749			22.92		73,403			17.63		82,609			17.11
Exercised		(111,423	)		14.97		(79,638	)		14.70		(23,659	)		10.22
Forfeited		(541	)		18.36		(32,360	)		20.69		(59,685	)		19.02
Outstanding, ending		587,961			14.83		623,176			13.88		661,771			13.89
Exercisable, ending		385,372					405,832					420,429
Weighted average fair value per option of options granted during the period	$	7.31				$	5.11				$	5.68

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

			Options Outstanding
					Weighted				Options Exercisable
					Average		Weighted				Weighted
					Remaining		Average				Average
Range of			Number		Contractual		Exercise		Number		Exercise
Exercise Prices			Outstanding		Life		Price		Exercisable		Price
$7.99	to	$8.93		35,040		3.84	$	8.18		35,040	$	8.18
$9.00	to	$9.30		160,707		3.82		9.22		147,200		9.22
$15.00	to	$16.85		168,164		3.64		15.69		147,291		15.69
$17.10	to	$18.00		145,551		7.56		17.25		55,341		17.25
$21.71	to	$31.53		78,499		9.09		21.71		500		21.71
				587,961						385,372

Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity [Table Text Block]

	2016		2015		2014
Shares granted		18,711		23,408		24,811
Shares purchased		20,192		24,033		25,321
Weighted average fair value per share granted	$	3.28	$	2.39	$	2.37