Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Note 9 - Fair Value Measurements - Summary of Fair Value Measurements by Level (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted cash and cash equivalents	$ 11,673	$ 8,303	$ 5,254
Available-for-sale securities	172,593	166,395
Corporate Debt Securities [Member]
Available-for-sale securities	67,632	65,461
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	21,436	26,218
Fair Value, Measurements, Recurring [Member]
Cash and cash equivalents	43,247	59,118
Restricted cash and cash equivalents	11,673	8,303
Total financial assets	367,736	372,901
Fair Value, Measurements, Recurring [Member] \| Equity Securities [Member]
Available-for-sale securities	140,223	139,085
Fair Value, Measurements, Recurring [Member] \| Corporate Debt Securities [Member]
Available-for-sale securities	67,632	65,461
Fair Value, Measurements, Recurring [Member] \| Asset-backed Securities [Member]
Available-for-sale securities	62,068	53,544
Fair Value, Measurements, Recurring [Member] \| US Treasury Securities [Member]
Available-for-sale securities	21,457	21,172
Fair Value, Measurements, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	21,436	26,218
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	43,247	59,118
Restricted cash and cash equivalents	11,673	8,303
Total financial assets	264,521	270,751
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Equity Securities [Member]
Available-for-sale securities	140,223	139,085
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Corporate Debt Securities [Member]
Available-for-sale securities	47,921	43,073
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Asset-backed Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US Treasury Securities [Member]
Available-for-sale securities	21,457	21,172
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents
Restricted cash and cash equivalents
Total financial assets	103,215	102,150
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Equity Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Corporate Debt Securities [Member]
Available-for-sale securities	19,711	22,388
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Asset-backed Securities [Member]
Available-for-sale securities	62,068	53,544
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US Treasury Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	$ 21,436	$ 26,218