Investments - Schedule of Pre-Tax Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Net Investment Income [Line Items]
Net investment income earned	$ 160,481	$ 138,655	$ 453,031	$ 387,314
Investment expenses	(5,342)	(5,402)	(16,763)	(16,386)
Fixed income securities
Net Investment Income [Line Items]
Net investment income earned	137,589	117,242	398,857	338,057
Commercial mortgage loans (“CMLs”)
Net Investment Income [Line Items]
Net investment income earned	4,148	3,999	12,463	11,375
Equity securities
Net Investment Income [Line Items]
Net investment income earned	5,376	5,164	15,098	13,639
Short-term investments
Net Investment Income [Line Items]
Net investment income earned	3,384	5,712	12,081	17,212
Alternative investments
Net Investment Income [Line Items]
Net investment income earned	15,187	11,769	30,670	22,852
Other investments
Net Investment Income [Line Items]
Net investment income earned	$ 139	$ 171	$ 625	$ 565

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.