Note F - Long-term Debt (Details Textual) - USD ($) $ in Thousands							3 Months Ended			9 Months Ended
	May 05, 2021	May 11, 2020	Apr. 14, 2020	May 07, 2019	Jan. 09, 2018	Apr. 17, 2017	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Letters of Credit Outstanding, Amount							$ 0			$ 0
Interest Expense, Debt, Total							63	$ 37		300	$ 400
Gain (Loss) on Extinguishment of Debt, Total										10,000	$ (0)
Standby Letters of Credit [Member]
Long-term Line of Credit, Total							1,100			1,100
Texas Capital Facility [Member]
Long-term Line of Credit, Total							13,100			13,100		$ 17,100
Line of Credit Facility, Remaining Borrowing Capacity							800			$ 800
Texas Capital Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 15,000	$ 19,000			$ 22,000
Debt Instrument, Term, Extension Period (Year)	1 year	1 year		1 year	1 year
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage						0.50%
Line of Credit Facility, Collateral Fees, Percentage						0.50%
Interest Expense, Debt, Total							$ 100
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
Gain (Loss) on Extinguishment of Debt, Total									$ 10,000