Note 10 - Fair Value Measurements - Summary of Fair Value Measurements by Level (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Restricted cash and cash equivalents	$ 16,198	$ 12,136	$ 11,409
Available-for-sale securities (USD)	142,647	172,100
Corporate Debt Securities [Member]
Available-for-sale securities (USD)	13,885	18,843
Asset-Backed Securities [Member]
Available-for-sale securities (USD)	494	1,469
Fair Value, Recurring [Member]
Cash and cash equivalents	58,667	107,607
Restricted cash and cash equivalents	16,198	12,136
Total financial assets	340,656	431,909
Fair Value, Recurring [Member] \| Equity Securities [Member]
Marketable equity securities	123,144	140,066
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Available-for-sale securities (USD)	64,894	81,779
Fair Value, Recurring [Member] \| Asset-Backed Securities [Member]
Available-for-sale securities (USD)	22,931	34,770
Fair Value, Recurring [Member] \| US Treasury Securities [Member]
Available-for-sale securities (USD)	50,051	47,628
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities (USD)	4,771	7,923
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	58,667	107,607
Restricted cash and cash equivalents	16,198	12,136
Total financial assets	297,922	357,442
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Equity Securities [Member]
Marketable equity securities	123,144	140,066
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Corporate Debt Securities [Member]
Available-for-sale securities (USD)	48,525	50,005
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Asset-Backed Securities [Member]
Available-for-sale securities (USD)	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US Treasury Securities [Member]
Available-for-sale securities (USD)	50,051	47,628
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities (USD)	1,337	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents	0	0
Restricted cash and cash equivalents	0	0
Total financial assets	42,734	74,467
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Equity Securities [Member]
Marketable equity securities	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Corporate Debt Securities [Member]
Available-for-sale securities (USD)	16,369	31,774
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Asset-Backed Securities [Member]
Available-for-sale securities (USD)	22,931	34,770
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US Treasury Securities [Member]
Available-for-sale securities (USD)	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities (USD)	$ 3,434	$ 7,923

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

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Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, 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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