Investments - Schedule of Fair Value and Gross Pre-Tax Net Unrealized Loss of Securities by Length of Time (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
AFS Fair Value, Less than 12 Months	$ 3,083,692	$ 1,121,478
AFS Unrealized Losses, Less than 12 months	(41,595)	(13,646)
AFS Fair Value, 12 months or longer	2,104,981	2,619,304
AFS Unrealized Losses, 12 months or longer	(210,607)	(208,472)
AFS Fair Value	5,188,673	3,740,782
AFS Unrealized Losses	(252,202)	(222,118)
U.S. government and government agencies
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
AFS Fair Value, Less than 12 Months	52,769	28,710
AFS Unrealized Losses, Less than 12 months	(686)	(57)
AFS Fair Value, 12 months or longer	96,350	110,826
AFS Unrealized Losses, 12 months or longer	(15,298)	(14,721)
AFS Fair Value	149,119	139,536
AFS Unrealized Losses	(15,984)	(14,778)
Foreign government
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
AFS Fair Value, Less than 12 Months	7,412	0
AFS Unrealized Losses, Less than 12 months	(26)	0
AFS Fair Value, 12 months or longer	7,836	9,058
AFS Unrealized Losses, 12 months or longer	(864)	(797)
AFS Fair Value	15,248	9,058
AFS Unrealized Losses	(890)	(797)
Obligations of states and political subdivisions
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
AFS Fair Value, Less than 12 Months	73,677	53,076
AFS Unrealized Losses, Less than 12 months	(860)	(604)
AFS Fair Value, 12 months or longer	182,590	230,441
AFS Unrealized Losses, 12 months or longer	(21,590)	(23,279)
AFS Fair Value	256,267	283,517
AFS Unrealized Losses	(22,450)	(23,883)
Corporate securities
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
AFS Fair Value, Less than 12 Months	755,727	128,218
AFS Unrealized Losses, Less than 12 months	(10,554)	(3,070)
AFS Fair Value, 12 months or longer	641,057	830,001
AFS Unrealized Losses, 12 months or longer	(68,396)	(68,792)
AFS Fair Value	1,396,784	958,219
AFS Unrealized Losses	(78,950)	(71,862)
CLO and other ABS
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
AFS Fair Value, Less than 12 Months	1,056,123	573,832
AFS Unrealized Losses, Less than 12 months	(15,205)	(6,993)
AFS Fair Value, 12 months or longer	384,607	462,469
AFS Unrealized Losses, 12 months or longer	(27,179)	(27,866)
AFS Fair Value	1,440,730	1,036,301
AFS Unrealized Losses	(42,384)	(34,859)
RMBS
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
AFS Fair Value, Less than 12 Months	944,556	283,926
AFS Unrealized Losses, Less than 12 months	(11,813)	(1,913)
AFS Fair Value, 12 months or longer	569,997	672,455
AFS Unrealized Losses, 12 months or longer	(64,204)	(59,421)
AFS Fair Value	1,514,553	956,381
AFS Unrealized Losses	(76,017)	(61,334)
CMBS
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
AFS Fair Value, Less than 12 Months	193,428	53,716
AFS Unrealized Losses, Less than 12 months	(2,451)	(1,009)
AFS Fair Value, 12 months or longer	222,544	304,054
AFS Unrealized Losses, 12 months or longer	(13,076)	(13,596)
AFS Fair Value	415,972	357,770
AFS Unrealized Losses	$ (15,527)	$ (14,605)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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