Note E - Stock Based Compensation - Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Outstanding, shares (in shares) | shares	45,068
Outstanding, weighted-average exercise price (in dollars per share) | $ / shares	$ 10.79
Granted, shares (in shares) | shares
Granted, weighted-average exercise price (in dollars per share) | $ / shares
Exercised, shares (in shares) | shares	(16,000)
Exercised, weighted-average exercise price (in dollars per share) | $ / shares	$ 10.47
Cancelled/forfeited/expired, shares (in shares) | shares	(63)
Cancelled/forfeited/expired, weighted-average exercise price (in dollars per share) | $ / shares	$ 10.90
Outstanding, shares (in shares) | shares	29,005
Outstanding, weighted-average exercise price (in dollars per share) | $ / shares	$ 10.96
Outstanding, weighted-average remaining contractual term (Year)	3 years 324 days
Outstanding, aggregate intrinsic value | $	$ 736,448	[1]
Exercisable, shares (in shares) | shares	29,005
Exercisable, weighted-average exercise price (in dollars per share) | $ / shares	$ 10.96
Exercisable, weighted-average remaining contractual term (Year)	3 years 324 days
Exercisable, aggregate intrinsic value | $	$ 736,448	[1]

[1] The intrinsic value of a stock option is the amount by which the market value of the underlying stock exceeds the exercise price of the option. The per share market value of our common stock, as determined by the closing price on May 29, 2018, was $36.35.