Note 11 - Summary of Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Balance, outstanding (in shares)	72,400	84,600	121,600
Balance, outstanding (in dollars per share)	$ 5.16	$ 5.04	$ 4.53
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0	12,000
Granted (in dollars per share)			$ 6.87
Forfeited or expired (in shares)	(2,000)
Forfeited or expired (in dollars per share)	$ 4.96
Exercised (in shares)	(2,000)	(12,200)	(49,000)
Exercised (in dollars per share)	$ 4.96	$ 4.32	$ 4.23
Balance, outstanding (in shares)	68,400	72,400	84,600
Balance, outstanding (in dollars per share)	$ 5.17	$ 5.16	$ 5.04
Exercisable at end of year (in shares)	68,400	72,400	84,600
Exercisable at end of year (in dollars per share)	$ 5.17	$ 5.16	$ 5.04
Weighted average grant-date fair value of stock options granted (in dollars per share)			$ 0.97