Note O - Employee and Director Benefit Plans - Reconciliation of Accumulated Post-retirement Benefit Obligation (Details) - Other Postretirement Benefits Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated post-retirement benefit obligation	$ 3,571
Service cost	88	$ 171	$ 153
Interest cost	107	136	$ 135
Actuarial gain	(604)
Employer contributions	20
Accumulated post-retirement benefit obligation	$ 3,182	$ 3,571