Note A - Summary of Significant Accounting Policies - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amortized Cost	$ 68,785	$ 78,562
Fair Value	68,981	78,733
Gross Unrealized Gains	196	176
Gross Unrealized Losses	0	5
Nontaxable Municipal Bonds [Member]
Amortized Cost	42,817	39,313
Fair Value	43,013	39,484
Gross Unrealized Gains	196	176
Gross Unrealized Losses	0	5
Variable Rate Demand Obligation [Member]
Amortized Cost	25,968	39,249
Fair Value	25,968	39,249
Gross Unrealized Gains	0	0
Gross Unrealized Losses	$ 0	$ 0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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