Note H - Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Expected Future Benefit Payment, Year One	$ 10,796
Defined Benefit Plan, Period Of Operating, History and Sufficient Trading Volume of Invested Entity (Year)	5 years
Minimum [Member]
Defined Benefit Plan, Period to Meet Goals (Year)	3 years
Maximum [Member]
Defined Benefit Plan, Period to Meet Goals (Year)	5 years
Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Benefits Paid	$ 10,495	$ 10,382
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	198,586	189,807
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year	3,500
Qualified Plan I [Member] | Pension Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment, Year One	$ 1,800
Defined Benefit Plan, Amortization Period (Year)	17 years 109 days
Qualified Plan II [Member] | Pension Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment, Year One	$ 2,200
Defined Benefit Plan, Amortization Period (Year)	27 years
Restoration Pension Plan [Member] | Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Benefits Paid	$ 1,700
Restoration Plan [Member] | Pension Plan [Member]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	$ 28,700	$ 27,600