Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

Summary of Investments

Investments consist of the following as of December 31, 2022 and 2021 (dollars in thousands):

	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

	December 31, 2021
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Municipal bonds	$	5,028	$	-	$	(1	)	$	5,027
Non-governmental debt securities		168,623		27		(184	)		168,466
Treasury and federal agencies		720		-		-			720
Total short-term investments (available for sale)	$	174,371	$	27	$	(185	)	$	174,213

Schedule of Available-for-Sale Investments

A schedule of available-for-sale investments segregated by their original stated terms to maturity as of December 31, 2022 and 2021 are as follows (dollars in thousands):

	Less than one year		One to five years		Six to ten years		Greater than ten years		Total
Original stated term to maturity of available-for-sale-    investments as of December 31, 2022	$	188,472	$	210,843	$	-	$	-	$	399,315
Original stated term to maturity of available-for-sale-    investments as of December 31, 2021	$	133,728	$	40,485	$	-	$	-	$	174,213

Schedule of Maintenance Fee Payment to our equity affiliate

We make periodic operating maintenance payments to our equity affiliate. The total fees recorded for the years ended December 31, 2022, 2021 and 2020 were as follows (dollars in thousands):

For the year ended December 31, 2022	$	1,578
For the year ended December 31, 2021	$	1,726
For the year ended December 31, 2020	$	1,596