Note 13 - Stock Option Plans - Stock Option Activity (Details)	12 Months Ended		168 Months Ended
	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 $ / shares shares	Dec. 31, 2016 $ / shares shares
Options outstanding at January 1 (in shares) | shares	274,500	274,500
Options cancelled (in shares) | shares	0	(8,000)	(240,680)
Options exercised (in shares) | shares	(12,000)	(4,000)	(740,320)
Options granted (in shares) | shares	42,000	12,000	1,285,500
Options outstanding at December 31 (in shares) | shares	304,500	274,500	304,500
Options available for grant at December 31 (in shares) | shares	834,000	876,000	834,000
Options exercisable at December 31 (in shares) | shares	256,500	254,500	256,500
Granted (in dollars per share)	$ 3.78	$ 2.97
Exercised (in dollars per share)	1.18	2.08
Outstanding (in dollars per share)	2.06	1.76	$ 2.06
Exercisable at December 31 (in dollars per share)	1.76	1.72	1.76
Minimum [Member]
Granted (in dollars per share)	3.50
Exercised (in dollars per share)	0.69
Outstanding (in dollars per share)	0.69	0.69	0.69
Maximum [Member]
Granted (in dollars per share)	3.89
Exercised (in dollars per share)	1.66
Outstanding (in dollars per share)	$ 3.89	$ 3.84	$ 3.89