Investments - Additional Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($) security	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Investments
Accrued investment income | $	$ 26,711		$ 24,062
Number of debt securities for which there is an allowance for credit losses | security	11
Losses on fixed income securities | $	$ 0	$ 2,000
Number of debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded | security	1,134
Unrealized loss | $	$ 160,796		214,396
Unrealized losses as percentage of fixed income portfolio cost basis	5.00%
Unrealized losses relative to total invested assets (as a percent)	4.00%
Number of unrealized loss positions | security	1,134
Number of securities in unrealized loss positions for 12 months or longer | security	1,045
Fixed Income Securities
Investments
Accrued investment income | $	$ 26,000		$ 23,000