Note H - Income Taxes - Reconciliation of Statutory Rate to Effective Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statutory rate	21.00%	21.00%	21.00%
State tax, net of federal benefit	1.70%	0.70%	2.60%
Tax exempt interest and dividends	(0.10%)	(0.10%)	(0.60%)
Other	(0.90%)	0.90%	0.80%
Effective rate	21.70%	22.50%	23.80%