Investments - Schedule of Investments Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Investments available for sale
Amortized Cost	$ 5,325,085	$ 5,184,856
Unrealized Gains	11,188	4,273
Unrealized Losses	(386,237)	(447,504)
Fair Value	4,950,036	4,741,625
U.S. Treasury securities
Investments available for sale
Amortized Cost	497,267	584,173
Unrealized Gains	843	341
Unrealized Losses	(22,326)	(28,076)
Fair Value	475,784	556,438
U.S. agency securities
Investments available for sale
Amortized Cost	12,696	49,059
Unrealized Gains	8	7
Unrealized Losses	(14)	(8)
Fair Value	12,690	49,058
U.S. agency mortgage-backed securities
Investments available for sale
Amortized Cost	950,645	898,675
Unrealized Gains	1,286	258
Unrealized Losses	(101,807)	(115,190)
Fair Value	850,124	783,743
Municipal debt securities
Investments available for sale
Amortized Cost	650,470	661,934
Unrealized Gains	5,489	2,010
Unrealized Losses	(46,949)	(61,254)
Fair Value	609,010	602,690
Non-U.S. government securities
Investments available for sale
Amortized Cost	69,606	69,651
Unrealized Gains	0	0
Unrealized Losses	(6,588)	(7,252)
Fair Value	63,018	62,399
Corporate debt securities
Investments available for sale
Amortized Cost	1,575,643	1,546,513
Unrealized Gains	3,040	1,195
Unrealized Losses	(116,087)	(133,387)
Fair Value	1,462,596	1,414,321
Residential and commercial mortgage securities
Investments available for sale
Amortized Cost	601,606	577,915
Unrealized Gains	208	390
Unrealized Losses	(59,801)	(66,481)
Fair Value	542,013	511,824
Asset-backed securities
Investments available for sale
Amortized Cost	680,460	660,345
Unrealized Gains	314	72
Unrealized Losses	(32,665)	(35,856)
Fair Value	648,109	624,561
Money market funds
Investments available for sale
Amortized Cost	286,692	136,591
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 286,692	$ 136,591

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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

+ References

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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