Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2023

Fair Value Disclosures [Abstract]

Summary of Investments

Investments consist of the following as of March 31, 2023 and December 31, 2022 (dollars in thousands):

	March 31, 2023
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Municipal bonds	$	3,005	$	-	$	(8	)	$	2,997
Non-governmental debt securities		216,958		53		(2,255	)		214,756
Treasury and federal agencies		205,023		43		(1,876	)		203,190
Total short-term investments (available for sale)	$	424,986	$	96	$	(4,139	)	$	420,943

	December 31, 2022
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Municipal bonds	$	3,016	$	-	$	(22	)	$	2,994
Non-governmental debt securities		222,575		37		(2,880	)		219,732
Treasury and federal agencies		179,068		6		(2,485	)		176,589
Total short-term investments (available for sale)	$	404,659	$	43	$	(5,387	)	$	399,315

Schedule of Maintenance Fee Payment to our equity affiliate

We make periodic operating maintenance payments to our equity affiliate. The total fees recorded during the quarters ended March 31, 2023 and 2022 were as follows (dollars in thousands):

	Maintenance Fee Payments
For the quarter ended March 31, 2023	$	431
For the quarter ended March 31, 2022	$	433