Note O - Employee and Director Benefit Plans - Components of Net Periodic Post-retirement Benefit Cost (Credit) (Details) - Other Postretirement Benefits Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Service cost	$ 88	$ 171	$ 153
Interest cost	107	136	135
Amortization of net gain	(129)
Amortization of prior service credit	(81)	(81)	(81)
Net periodic post-retirement benefit cost (credit)	$ (15)	$ 226	$ 207