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Investments - Schedule of Pre-Tax Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Net Investment Income [Line Items]
Net investment income earned	$ 127,968	$ 108,642	$ 248,659	$ 216,491
Fixed income securities
Net Investment Income [Line Items]
Net investment income earned	115,733	93,935	220,815	188,037
CMLs
Net Investment Income [Line Items]
Net investment income earned	3,761	3,145	7,376	5,939
Equity securities
Net Investment Income [Line Items]
Net investment income earned	4,908	1,877	8,475	6,785
Short-term investments
Net Investment Income [Line Items]
Net investment income earned	5,267	4,680	11,500	8,199
Alternative investments
Net Investment Income [Line Items]
Net investment income earned	4,004	10,517	11,083	17,398
Other investments
Net Investment Income [Line Items]
Net investment income earned	163	118	394	381
Investment expenses
Net Investment Income [Line Items]
Investment expenses	$ (5,868)	$ (5,630)	$ (10,984)	$ (10,248)

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