Note F - Long-term Debt (Details Textual) - USD ($) $ in Thousands	May 11, 2020	May 07, 2019	Jan. 09, 2018	Apr. 17, 2017	Mar. 31, 2020	Dec. 31, 2019
Letters of Credit Outstanding, Amount					$ 0
Standby Letters of Credit [Member]
Long-term Line of Credit, Total					1,700
Texas Capital Facility [Member]
Long-term Line of Credit, Total					$ 18,700	$ 18,700
Texas Capital Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity			$ 22,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage				0.50%
Line of Credit Facility, Collateral Fees, Amount				$ 100
Debt Instrument, Term, Extension Period (Year)		1 year	1 year
Texas Capital Credit Facility [Member] | Subsequent Event [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 19,000
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] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity				$ 20,000
Texas Capital Credit Facility [Member] | Standby Letters of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity				$ 5,000