Note 12 - Stock Option Plans (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

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

	2018					2017
Options outstanding at January 1				243,500					304,500
Options cancelled				(8,000	)				(18,000	)
Options exercised				(40,000	)				(60,000	)
Options granted				12,000					17,000
Options outstanding at December 31				207,500					243,500
Options available for grant at December 31				805,000					817,000
Options exercisable at December 31				179,000					206,500
Exercise price ranges per share:
Granted	$			7.80		$			3.86
Exercised	$	0.69	-	$3.89		$	1.52	-	$1.72
Outstanding	$	0.69	-	$7.80		$	0.69	-	$3.89
Weighted average exercise price per share:
Granted	$			7.80		$			3.86
Exercised	$			2.79		$			1.63
Outstanding at December 31	$			2.33		$			2.17
Exercisable at December 31	$			1.82		$			1.87

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

Range of Exercise Price			Number Outstanding		Wgt. Avg. Contractual Life Remaining (in yrs)	Wgt. Avg. Exercise Price		Aggregate Intrinsic Value
$0.69	-	$1.72		150,500	3.0	$	1.53	$	1,714,670
$2.97	-	$7.80		57,000	7.9	$	4.44	$	483,120
$0.69	-	$7.80		207,500	4.4	$	2.33	$	2,197,790

Range of Exercise Price			Number Exercisable		Wgt. Avg. Contractual Life Remaining (in yrs)	Wgt. Avg. Exercise Price		Aggregate Intrinsic Value
$0.69	-	$1.72		150,500	3.0	$	1.53	$	1,714,670
$2.97	-	$7.80		28,500	7.3	$	3.36	$	272,490
$0.69	-	$7.80		179,000	3.7	$	1.82	$	1,987,160