Note 10 - Stock Option Plans (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	201 9					201 8
Options outstanding at January 1				207,500					243,500
Options cancelled				(16,000	)				(8,000	)
Options exercised				(107,000	)				(40,000	)
Options granted				42,000					12,000
Options outstanding at December 31				126,500					207,500
Options available for grant at December 31				763,000					805,000
Options exercisable at December 31				84,500					179,000
Exercise price ranges per share:
Granted	$	19.99	-	$39.11		$			7.80
Exercised	$	0.69	-	$ 7.80		$	0.69	-	$ 3.89
Outstanding	$	1.52	-	$ 39.11		$	0.69	-	$ 7.80
Weighted average exercise price per share:
Granted	$			25.45		$			7.80
Exercised	$			1.97		$			2.79
Outstanding at December 31	$			8.94		$			2.33
Exercisable at December 31	$			2.21		$			1.82

Share-based Payment Arrangement, Option, Exercise Price Range [Table Text Block]

Options Outstanding:
Range of Exercise Price			Number Outstanding		Wgt. Avg. Contractual Life Remaining (in years)		Wgt. Avg. Exercise Price		Aggregate Intrinsic Value
$1.52	-	$1.72		67,500		1.5	$	1.59	$	2,588,850
$3.50	-	$39.11		59,000		8.6	$	17.35	$	1,332,740
$1.52	-	$39.11		126,500		4.8	$	8.94	$	3,921,590

Options Exercisable:
Range of Exercise Price			Number Exercisable		Wgt. Avg. Contractual Life Remaining (in years)		Wgt. Avg. Exercise Price		Aggregate Intrinsic Value
$1.52	-	$1.72		67,500		1.5	$	1.59	$	2,588,850
$3.50	-	$7.80		17,000		7.5	$	4.70	$	599,040
$1.52	-	$7.80		84,500		2.7	$	2.21	$	3,187,890