Note 13 - Stock Based Compensation - Stock Option Activity (Details) - 2005 Stock Option Plan [Member]	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Beginning balance, options outstanding (in shares) | shares	187,000
Beginning balance, weighted average exercise price (in dollars per share) | $ / shares	$ 7.78
Granted, options outstanding (in shares) | shares
Granted, weighted average exercise price (in dollars per share) | $ / shares
Exercised, options outstanding (in shares) | shares	(23,800)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 8.33
Expired, options outstanding (in shares) | shares	(31,500)
Expired, weighted average exercise price (in dollars per share) | $ / shares	$ (10.79)
Vested, options outstanding (in shares) | shares	(15,000)
Vested, weighted average exercise price (in dollars per share) | $ / shares	$ 6.90
Ending balance, options outstanding (in shares) | shares	116,700
Ending balance, weighted average exercise price (in dollars per share) | $ / shares	$ 6.90
Balance, aggregate intrinsic value | $	$ 576,498	[1]
Balance, weighted average contractual term (Year)	5 years 354 days
Exercisable, options outstanding (in shares) | shares	92,100
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 6.90
Exercisable, aggregate intrinsic value | $	$ 454,974	[1]
Exercisable, weighted average contractual term (Year)	5 years 354 days

[1] The aggregate intrinsic value of a stock option in the table above represents the total pre-tax intrinsic value (the amount by which the current market value of the underlying stock exceeds the exercise price of the option) that would have been received by the option holders had all option holders exercised their options on December 31, 2018.