Note 4 - Marketable Securities

3 Months Ended

Mar. 31, 2022

Notes to Financial Statements

Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]

NOTE 4 — MARKETABLE SECURITIES

Marketable securities are presented at fair value and include investments in debt securities classified as available for sale. All marketable securities have maturities of less than a year. Investment in marketable securities is comprised of the following:

	March 31, 2022									December 31, 2021
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value		Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
	(Dollars in thousands)									(Dollars in thousands)
Debt security type:
Corporate bonds	$	31,002	$	—	$	(127	)	$	31,043	$	32,302	$	—	$	(36	)	$	32,529
Commercial paper		9,375		—		—			9,375		8,891		—		—			8,891
Money market funds		4,049		—		—			4,049		3,686		—		—			3,686
Foreign issuers		1,010		—		(11	)		1,005		1,920		—		(4	)		1,923
Municipal bonds		1,497		—		(4	)		1,504		—		—		—			—
Total debt securities available for sale	$	46,933	$	—	$	(142	)	$	46,976	$	46,799	$	—	$	(40	)	$	47,029

As of March 31, 2022 and December 31, 2021, approximately $4.0 million and $3.7 million of debt securities, respectively, were classified under "Cash and cash equivalents" in the condensed consolidated balance sheets as they met all applicable classification criteria.

The following table summarizes the fair value and gross unrealized losses of debt securities with unrealized losses aggregated by security type and length of time that the fair value had been below amortized cost, on an individual security basis:

	March 31, 2022									December 31, 2021
	Less than 12 months					Greater than 12 months				Less than 12 months					Greater than 12 months
	Fair value		Gross unrealized loss			Fair value		Gross unrealized loss		Fair value		Gross unrealized loss			Fair value		Gross unrealized loss
	(Dollars in thousands)									(Dollars in thousands)
Debt security type:
Corporate bonds	$	31,043	$	(127	)	$	—	$	—	$	32,529	$	(36	)	$	—	$	—
Commercial paper		9,375		—			—		—		8,891		—			—		—
Money market funds		4,049		—			—		—		3,686		—			—		—
Foreign issuers		1,005		(11	)		—		—		1,923		(4	)		—		—
Municipal bonds		1,504		(4	)		—		—		—		—			—		—
Total debt securities available for sale	$	46,976	$	(142	)	$	—	$	—	$	47,029	$	(40	)	$	—	$	—

There were no sales of investments in debt securities during the three months ended March 31, 2022 and the year ended December 31, 2021.