Note O - Employee and Director Benefit Plans - Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net gain	$ (394)	$ (459)	$ 1,160
Other Postretirement Benefits Plan [Member]
Net gain	816	440	11
Prior service charge	616	680	622
Total other comprehensive income	$ 1,432	$ 1,120	$ 633