Investments - Additional Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2025 USD ($) security	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Investments
Accrued investment income | $	$ 29,584		$ 28,319
Number of debt securities for which there is an allowance for credit losses | security	12
Number of debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded | security	1,077
Unrealized loss | $	$ 150,368		224,611
Unrealized losses as percentage of fixed income portfolio cost basis	4.00%
Unrealized losses relative to total invested assets (as a percent)	3.00%
Number of unrealized loss positions | security	1,077
Number of securities in unrealized loss positions for 12 months or longer | security	926
Maximum
Investments
Losses on fixed income securities | $	$ 1,000	$ 0
Fixed Income Securities
Investments
Accrued investment income | $	$ 28,000		$ 27,000