Investments - Additional Information (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) security	Dec. 31, 2021 USD ($)
Investment Holdings [Line Items]
Accrued investment income	$ 21,259,000	$ 17,505,000
Unrealized loss	280,222,000	16,891,000
Fixed Income Securities
Investment Holdings [Line Items]
Accrued investment income	$ 20,200	16,400
Number of debt securities for which there is an allowance for credit losses | security	14
Losses on fixed income securities	$ 100,000	0
Number of debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded | security	1,473
Unrealized loss	$ 280,200,000
Unrealized losses as percentage of fixed income portfolio cost basis	9.50%
Unrealized losses relative to total invested assets (as a percent)	8.60%
Number of unrealized loss positions | security	1,473
Number of securities in unrealized loss positions for 12 months or longer | security	518
ABS/CMBS/MBS
Investment Holdings [Line Items]
Percentage of securities of portfolio rated with highest credit rating by by one or more major rating agency	83.00%
Unrealized loss	$ 35,444,000	2,339,000
Municipal
Investment Holdings [Line Items]
General obligations to state and local governments Percentage	46.00%
Revenue based obligations percentage	54.00%
Percentage of securities of portfolio rated as AA or better	88.00%
Percentage of securities of portfolio rated as A or better	99.00%
Unrealized loss	$ 102,725,000	$ 4,281,000