Note D - Stock-based Compensation - Stock Option Activity by Exercise Price (Details)	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Shares under exercisable options (in shares)	46,131
Shares under outstanding options (in shares)	46,131
Weighted-average remaining contractual term (Year)	3 years 146 days
Exercise Price 1 [Member]
Shares under exercisable options (in shares)	15,000
Exercise price (in dollars per share) | $ / shares	$ 10.44
Shares under outstanding options (in shares)	15,000
Weighted-average remaining contractual term (Year)	255 days
Exercise Price 2 [Member]
Shares under exercisable options (in shares)	25,600
Exercise price (in dollars per share) | $ / shares	$ 10.90
Shares under outstanding options (in shares)	25,600
Weighted-average remaining contractual term (Year)	4 years 328 days
Exercise Price 3 [Member]
Shares under exercisable options (in shares)	5,531
Exercise price (in dollars per share) | $ / shares	$ 11.22
Shares under outstanding options (in shares)	5,531
Weighted-average remaining contractual term (Year)	3 years 146 days