Note F - Long-term Debt (Details Textual) - USD ($) $ in Thousands							3 Months Ended
	May 05, 2021	May 11, 2020	Apr. 14, 2020	May 07, 2019	Jan. 09, 2018	Apr. 17, 2017	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Letters of Credit Outstanding, Amount							$ 0
Interest Expense, Debt, Total							100	$ 200
Standby Letters of Credit [Member]
Long-term Line of Credit, Total							1,800		$ 1,800
Texas Capital Facility [Member]
Long-term Line of Credit, Total							17,100		$ 17,100
Line of Credit Facility, Remaining Borrowing Capacity							100
Texas Capital Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 19,000			$ 22,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage						0.50%
Line of Credit Facility, Collateral Fees, Percentage						0.50%
Line of Credit Facility, Collateral Fees, Amount							100
Debt Instrument, Term, Extension Period (Year)		1 year		1 year	1 year
Texas Capital Credit Facility [Member] | Subsequent Event [Member]
Long-term Line of Credit, Total	$ 13,100
Line of Credit Facility, Maximum Borrowing Capacity	$ 15,000
Debt Instrument, Term, Extension Period (Year)	1 year
Texas Capital Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate						1.95%
Texas Capital Credit Facility [Member] | Prime Rate [Member]
Debt Instrument, Basis Spread on Variable Rate						0.75%
Texas Capital Credit Facility [Member] | Standby Letters of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity						$ 5,000
Texas Capital Credit Facility [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity						$ 20,000
Paycheck Protection Program CARES Act [Member]
Proceeds from Notes Payable, Total			$ 10,000
Debt Instrument, Due Within Twelve Months If Not Forgiven							$ 8,700