Note 8 - Investments in Marketable Securities - Marketable Securities and Restricted Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Restricted investments available for sale, amortized cost	$ 176,067	$ 167,277
Restricted investments available for sale, fair value	172,593	166,395
Investments available for sale, amortized cost	206,243	197,453
Investments available for sale, fair value	312,816	305,480
Equity Securities [Member]
Unrestricted investments available for sale, amortized cost	30,176	30,176
Unrestricted investments available for sale, fair value	140,223	139,085
Corporate Debt Securities [Member]
Restricted investments available for sale, amortized cost	69,439	65,107
Restricted investments available for sale, fair value	67,632	65,461
Collateralized Mortgage Backed Securities [Member]
Restricted investments available for sale, amortized cost	62,772	54,030
Restricted investments available for sale, fair value	62,068	53,544
US Government Corporations and Agencies Securities [Member]
Restricted investments available for sale, amortized cost	22,038	21,685
Restricted investments available for sale, fair value	21,457	21,172
US States and Political Subdivisions Debt Securities [Member]
Restricted investments available for sale, amortized cost	21,818	26,455
Restricted investments available for sale, fair value	$ 21,436	$ 26,218

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

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-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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