Investments - Schedule of Available For Sale Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Amortized Cost
Amortized Cost	$ 5,809,829	$ 5,586,730
Fair Value
Fair Value	5,454,983	5,263,739
U.S. Treasury securities
Amortized Cost
Due in 1 year	669,532
Due after 1 but within 5 years	296,652
Due after 5 but within 10 years	38,816
Due after 10 years	14,443
Subtotal	1,019,443
Amortized Cost	1,019,443	1,014,076
Fair Value
Due in 1 year	666,822
Due after 1 but within 5 years	284,595
Due after 5 but within 10 years	35,074
Due after 10 years	12,685
Subtotal	999,176
Fair Value	999,176	996,382
Municipal debt securities
Amortized Cost
Due in 1 year	10,148
Due after 1 but within 5 years	86,662
Due after 5 but within 10 years	125,670
Due after 10 years	345,889
Subtotal	568,369
Amortized Cost	568,369	585,047
Fair Value
Due in 1 year	9,992
Due after 1 but within 5 years	83,246
Due after 5 but within 10 years	116,787
Due after 10 years	314,371
Subtotal	524,396
Fair Value	524,396	547,258
Non-U.S. government securities:
Amortized Cost
Due in 1 year	4,800
Due after 1 but within 5 years	31,896
Due after 5 but within 10 years	8,338
Due after 10 years	32,336
Subtotal	77,370
Amortized Cost	77,370	77,516
Fair Value
Due in 1 year	4,715
Due after 1 but within 5 years	30,319
Due after 5 but within 10 years	6,856
Due after 10 years	24,141
Subtotal	66,031
Fair Value	66,031	67,447
Corporate debt securities:
Amortized Cost
Due in 1 year	160,824
Due after 1 but within 5 years	405,414
Due after 5 but within 10 years	536,015
Due after 10 years	146,035
Subtotal	1,248,288
Amortized Cost	1,248,288	1,380,533
Fair Value
Due in 1 year	159,044
Due after 1 but within 5 years	384,152
Due after 5 but within 10 years	491,049
Due after 10 years	117,731
Subtotal	1,151,976
Fair Value	1,151,976	1,297,055
U.S. agency mortgage-backed securities
Amortized Cost
Amortized Cost	876,049	922,907
Fair Value
Fair Value	757,590	821,346
Residential and commercial mortgage securities
Amortized Cost
Amortized Cost	550,708	571,163
Fair Value
Fair Value	498,987	517,940
Asset-backed securities
Amortized Cost
Amortized Cost	468,228	584,168
Fair Value
Fair Value	455,453	564,995
Money market funds
Amortized Cost
Amortized Cost	1,001,374	444,121
Fair Value
Fair Value	$ 1,001,374	$ 444,121

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
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