3. Restricted Marketable Securities (Details) - Available For Sale - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 38,916	$ 157,158
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	88
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,483	1,705
Debt Securities, Available-for-Sale, Allowance for Credit Loss	3	46
Restricted marketable securities	200,243	198,310
Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	259,199	253,834
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	58,957	55,480
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	44
Restricted marketable securities	$ 200,243	198,310
Minimum [Member] | Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Contractual maturities of Debt securities, Available-for-sale, range start (in years)	7 years
Maximum [Member] | Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Contractual Maturities Of Debt securities, Available-for-sale, Range End (In Years)	15 years
Foreign government obligations [Member] | Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 63,752	65,202
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	14,842	13,963
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	10
Restricted marketable securities	48,910	51,229
Supranational debt [Member] | Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	25,460	17,688
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2,561	2,349
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	0
Restricted marketable securities	22,900	15,339
U.S. debt [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	10,000	45,625
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	88
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,483	1,614
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	10
U.S. debt [Member] | Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	145,573	146,484
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	35,457	33,129
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	29
Restricted marketable securities	110,116	113,326
U.S. government obligations [Member] | Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	24,414	24,460
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	6,097	6,039
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	5
Restricted marketable securities	$ 18,317	$ 18,416