Note 4 - Marketable Securities

6 Months Ended

Jun. 30, 2021

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:

	June 30, 2021
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
	(Dollars in thousands)
Debt security type:
Corporate bonds	$	30,472	$	—	$	(10	)	$	30,707
Commercial paper		11,465		—		—			11,465
Money market funds		17,053		—		—			17,053
Foreign issuers		2,841		—		(1	)		2,849
Municipal bonds		920		—		—			938
Total debt securities available for sale	$	62,751	$	—	$	(11	)	$	63,012

As of June 30, 2021, approximately $17.1 million of debt securities 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:

	June 30, 2021
	Less than 12 months					Greater than 12 months
	Fair value		Gross unrealized loss			Fair value		Gross unrealized loss
	(Dollars in thousands)
Debt security type:
Corporate bonds	$	30,707	$	(10	)	$	—	$	—
Commercial paper		11,465		—			—		—
Money market funds		17,053		—			—		—
Foreign issuers		2,849		(1	)		—		—
Municipal bonds		938		—			—		—
Total debt securities available for sale	$	63,012	$	(11	)	$	—	$	—

There were no sales of investments in debt securities during the six months ended June 30, 2021 and 2020.