Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

Summary of Investments

Investments consist of the following as of June 30, 2024 and December 31, 2023 (dollars in thousands):

	June 30, 2024
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Non-governmental debt securities	$	244,985	$	80	$	(847	)	$	244,218
Treasury and federal agencies		302,912		19		(876	)		302,055
Total short-term investments (available for sale)	$	547,897	$	99	$	(1,723	)	$	546,273

	December 31, 2023
			Gross Unrealized
	Cost		Gain		(Loss)			Fair Value
Short-term investments (available for sale):
Non-governmental debt securities		245,886		719		(892	)		245,713
Treasury and federal agencies		239,859		393		(830	)		239,422
Total short-term investments (available for sale)	$	485,745	$	1,112	$	(1,722	)	$	485,135

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 June 30, 2024 and 2023 were as follows (dollars in thousands):

	Maintenance Fee Payments
For the quarter ended June 30, 2024	$	423
For the quarter ended June 30, 2023	$	414
For the year to date ended June 30, 2024	$	867
For the year to date ended June 30, 2023	$	845