Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

Summary of Investments

Investments consist of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands):

	September 30, 2023
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Non-governmental debt securities	$	227,417	$	-	$	(2,541	)	$	224,876
Treasury and federal agencies		207,083		-		(2,342	)		204,741
Total short-term investments (available for sale)	$	434,500	$	-	$	(4,883	)	$	429,617

	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 and years to date ended September 30, 2023 and 2022 were as follows (dollars in thousands):

	Maintenance Fee Payments
For the quarter ended September 30, 2023	$	411
For the quarter ended September 30, 2022	$	374
For the year to date ended September 30, 2023	$	1,256
For the year to date ended September 30, 2022	$	1,201