Note A - Overview and Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Balance at beginning of year	$ 666	$ 430
Net charges to expense	115	351
Amounts recovered against the allowance	(540)	(115)
Balance at end of year	$ 241	$ 666