Note 9 - Investments in Marketable Securities - Marketable Securities and Restricted Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Restricted investments available for sale, amortized cost	$ 173,056	$ 176,067
Restricted investments available for sale, fair value	172,807	172,593
Investments available for sale, amortized cost	203,232	206,243
Investments available for sale, fair value	319,868	312,816
Equity Securities [Member]
Unrestricted investments available for sale, amortized cost	30,176	30,176
Unrestricted investments available for sale, fair value	147,061	140,223
Corporate Debt Securities [Member]
Restricted investments available for sale, amortized cost	66,649	69,439
Restricted investments available for sale, fair value	66,819	67,632
Collateralized Mortgage Backed Securities [Member]
Restricted investments available for sale, amortized cost	64,601	62,772
Restricted investments available for sale, fair value	64,504	62,068
US Government Corporations and Agencies Securities [Member]
Restricted investments available for sale, amortized cost	20,091	22,038
Restricted investments available for sale, fair value	19,748	21,457
US States and Political Subdivisions Debt Securities [Member]
Restricted investments available for sale, amortized cost	21,715	21,818
Restricted investments available for sale, fair value	$ 21,736	$ 21,436

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=118939692&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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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).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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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
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