Note 11 - Stock Option Plan - Stock Option Plan (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Outstanding, Shares (in shares)	3,500	15,000
Outstanding, Weighted average exercise price (in dollars per share)	$ 5.94	$ 9.58
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0
Granted, Weighted average exercise price (in dollars per share)	$ 0	$ 0
Exercised, Shares (in shares)	(1,500)	(9,000)
Exercised, Weighted average exercise price (in dollars per share)	$ 4.58	$ 10.10
Forfeited, Shares (in shares)	(1,000)	(2,500)
Forfeited, Weighted average exercise price (in dollars per share)	$ 8.25	$ 12.75
Outstanding, Shares (in shares)	1,000	3,500
Outstanding, Weighted average exercise price (in dollars per share)	$ 5.74	$ 5.94