Note 11 - Stockholders' Equity - Summary of Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Balance, outstanding (in shares)	56,400	68,400	72,400	84,600
Balance, outstanding (in dollars per share)	$ 5.14	$ 5.17	$ 5.16	$ 5.04
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0	0
Granted (in dollars per share)
Forfeited or expired (in shares)		(12,000)	(2,000)
Forfeited or expired (in dollars per share)		$ 5.30	$ 4.96
Exercised (in shares)			(2,000)	(12,200)
Exercised (in dollars per share)			$ 4.96	$ 4.32
Balance, outstanding (in shares)		56,400	68,400	72,400
Balance, outstanding (in dollars per share)		$ 5.14	$ 5.17	$ 5.16
Exercisable at end of year (in shares)		56,400	68,400	72,400
Exercisable at end of year (in dollars per share)		$ 5.14	$ 5.17	$ 5.16