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Note 9 - Investments in Marketable Securities - Marketable Securities and Restricted Marketable Securities (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Unrestricted investments available for sale, equity, amortized cost | $ 24,734 | $ 24,734
Marketable equity securities | 123,040 | 111,117
Unrestricted investments available for sale, debt, amortized cost | 132,410 | 135,338
Unrestricted investments available for sale, debt, fair value | 124,316 | 127,727
Restricted marketable equity securities | 29,616 | 26,779
Investments available for sale, amortized cost | 187,081 | 189,648
Marketable Securities | 276,972 | 265,623
Equity Securities [Member] |  |
Unrestricted investments available for sale, equity, amortized cost | 30,176 | 30,176
Marketable equity securities | 123,040 | 111,117
Restricted investments available for sale, equity, amortized cost | 24,495 | 24,134
Restricted marketable equity securities | 29,616 | 26,779
Corporate Debt Securities [Member] |  |
Unrestricted investments available for sale, debt, amortized cost | 494 | 2,497
Unrestricted investments available for sale, debt, fair value | 484 | 2,441
Restricted investments available for sale, debt, amortized cost | 61,488 | 59,586
Restricted investments available for sale, debt, fair value | 59,398 | 57,731
US Government Corporations and Agencies Securities [Member] |  |
Unrestricted investments available for sale, debt, amortized cost | 0 | 2,990
Unrestricted investments available for sale, debt, fair value | 0 | 2,986
Restricted investments available for sale, debt, amortized cost | 47,323 | 46,771
Restricted investments available for sale, debt, fair value | 43,004 | 42,863
Asset-Backed Securities [Member] |  |
Restricted investments available for sale, debt, amortized cost | 19,026 | 19,388
Restricted investments available for sale, debt, fair value | 17,438 | 17,659
US States and Political Subdivisions Debt Securities [Member] |  |
Restricted investments available for sale, debt, amortized cost | 4,079 | 4,106
Restricted investments available for sale, debt, fair value | $ 3,992 | $ 4,047

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