Note 3 - Investments and Restricted Investments - Summaries of the Amortized Cost, Unrealized Gains, Unrealized Losses, and Fair Value by Investment Type (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Investments, available for sale, amortized cost	$ 17,009	$ 24,997
Investments, available for sale, gross unrealized gains	113	65
Investments, available for sale, gross unrealized losses	0	(167)
Investments, available for sale, estimated fair value	17,122	24,895
Restricted investments, held-to-maturity, amortized cost	114,171	114,648
Restricted investments, gross unrealized gains	761	299
Restricted investments, gross unrealized losses	(1,229)	(1,991)
Restricted investments, estimated fair value	113,703	112,956
US Treasury Securities [Member]
Investments, available for sale, amortized cost	17,009	24,997
Investments, available for sale, gross unrealized gains	113	65
Investments, available for sale, gross unrealized losses	0	(167)
Investments, available for sale, estimated fair value	17,122	24,895
Restricted investments, held-to-maturity, amortized cost	114,171	114,648
Restricted investments, gross unrealized gains	761	299
Restricted investments, gross unrealized losses	(1,229)	(1,991)
Restricted investments, estimated fair value	$ 113,703	$ 112,956

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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Amortized cost of 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 allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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