Investments - Schedule of Pre-Tax Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Net Investment Income [Line Items]
Net investment income earned	$ 150,167	$ 127,968	$ 292,550	$ 248,659
Investment expenses	(6,291)	(5,868)	(11,421)	(10,984)
Fixed income securities
Net Investment Income [Line Items]
Net investment income earned	134,641	115,733	261,268	220,815
Commercial mortgage loans ("CMLs")
Net Investment Income [Line Items]
Net investment income earned	4,086	3,761	8,315	7,376
Equity securities
Net Investment Income [Line Items]
Net investment income earned	5,520	4,908	9,722	8,475
Short-term investments
Net Investment Income [Line Items]
Net investment income earned	3,157	5,267	8,697	11,500
Alternative investments
Net Investment Income [Line Items]
Net investment income earned	8,608	4,004	15,483	11,083
Other investments
Net Investment Income [Line Items]
Net investment income earned	$ 446	$ 163	$ 486	$ 394

Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.