Marketable Securities - Available-For-Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Available-For-Sale Securities
Amortized Cost	$ 28,330	$ 29,444
Gross Unrealized Gain	36	434
Gross Unrealized (Losses)	(304)	0
Estimated Fair Value	28,062	29,878
Tax-exempt municipal securities
Available-For-Sale Securities
Amortized Cost	18,572	18,546
Gross Unrealized Gain	31	271
Gross Unrealized (Losses)	(232)	0
Estimated Fair Value	18,371	18,817
Corporate debt securities
Available-For-Sale Securities
Amortized Cost	9,758	10,898
Gross Unrealized Gain	5	163
Gross Unrealized (Losses)	(72)	0
Estimated Fair Value	$ 9,691	$ 11,061

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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