Investments - Additional Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($) security	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Investment Holdings [Line Items]
Accrued investment income	$ 19,355		$ 17,505
Unrealized loss	301,708		16,891
Fixed Income Securities
Investment Holdings [Line Items]
Accrued investment income	$ 18,400		$ 16,400
Number of debt securities for which there is an allowance for credit losses | security	18
Losses on fixed income securities	$ 100	$ 0
Number of debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded | security	1,543
Unrealized loss	$ 301,700
Unrealized losses as percentage of fixed income portfolio cost basis	10.80%
Unrealized losses relative to total invested assets (as a percent)	8.20%
Number of unrealized loss positions | security	1,543
Number of securities in unrealized loss positions for 12 months or longer | security	302