Investments - Schedule of Available For Sale Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Amortized Cost
Amortized Cost	$ 6,219,151	$ 6,231,018
Fair Value
Fair Value	5,966,537	5,876,721
U.S. Treasury securities:
Amortized Cost
Due in 1 year	94,020
Due after 1 but within 5 years	268,372
Due after 5 but within 10 years	21,709
Due after 10 years	14,490
Subtotal	398,591
Amortized Cost	398,591	561,853
Fair Value
Due in 1 year	92,725
Due after 1 but within 5 years	265,801
Due after 5 but within 10 years	20,340
Due after 10 years	12,595
Subtotal	391,461
Fair Value	391,461	547,290
Municipal debt securities
Amortized Cost
Due in 1 year	20,710
Due after 1 but within 5 years	91,433
Due after 5 but within 10 years	147,229
Due after 10 years	386,505
Subtotal	645,877
Amortized Cost	645,877	631,015
Fair Value
Due in 1 year	20,575
Due after 1 but within 5 years	89,634
Due after 5 but within 10 years	140,145
Due after 10 years	350,264
Subtotal	600,618
Fair Value	600,618	583,501
Non-U.S. government securities
Amortized Cost
Due in 1 year	6,529
Due after 1 but within 5 years	25,938
Due after 5 but within 10 years	7,696
Due after 10 years	32,098
Subtotal	72,261
Amortized Cost	72,261	81,631
Fair Value
Due in 1 year	6,455
Due after 1 but within 5 years	25,340
Due after 5 but within 10 years	6,545
Due after 10 years	23,826
Subtotal	62,166
Fair Value	62,166	69,798
Corporate debt securities:
Amortized Cost
Due in 1 year	165,479
Due after 1 but within 5 years	612,577
Due after 5 but within 10 years	990,216
Due after 10 years	200,700
Subtotal	1,968,972
Amortized Cost	1,968,972	1,887,647
Fair Value
Due in 1 year	164,573
Due after 1 but within 5 years	597,076
Due after 5 but within 10 years	973,327
Due after 10 years	173,191
Subtotal	1,908,167
Fair Value	1,908,167	1,783,046
U.S. agency mortgage-backed securities
Amortized Cost
Amortized Cost	1,265,904	1,249,259
Fair Value
Fair Value	1,172,715	1,125,436
Residential and commercial mortgage securities
Amortized Cost
Amortized Cost	484,715	519,613
Fair Value
Fair Value	454,381	478,086
Asset-backed securities
Amortized Cost
Amortized Cost	801,867	642,395
Fair Value
Fair Value	796,065	631,959
Money market funds
Amortized Cost
Amortized Cost	580,964	657,605
Fair Value
Fair Value	$ 580,964	$ 657,605

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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-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-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
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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