3. Restricted Marketable Securities (Details) - Available For Sale - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 265,869	$ 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	1,178	1,705
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	46
Restricted marketable securities	211,130	198,310
Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	260,245	253,834
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	49,118	55,480
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	44
Restricted marketable securities	$ 211,130	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)	6 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	$ 65,336	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	12,968	13,963
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	10
Restricted marketable securities	52,368	51,229
Supranational debt [Member] | Restricted Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	25,405	17,688
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	3	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2,058	2,349
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	0
Restricted marketable securities	23,350	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	1,178	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	145,113	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	28,956	33,129
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	29
Restricted marketable securities	116,157	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	24,391	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	5,136	6,039
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0	5
Restricted marketable securities	$ 19,255	$ 18,416