Investments - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($) security	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Investment Holdings [Line Items]
Accrued investment income	$ 21,118		$ 21,259
Unrealized loss	235,674		280,222
Fixed Income Securities
Investment Holdings [Line Items]
Accrued investment income	$ 20,000		20,000
Number of debt securities for which there is an allowance for credit losses | security	18
Losses on fixed income securities	$ 1,700	$ 100
Number of debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded | security	1,388
Unrealized loss	$ 236,000
Unrealized losses as percentage of fixed income portfolio cost basis	8.00%
Unrealized losses relative to total invested assets (as a percent)	7.00%
Number of unrealized loss positions | security	1,388
Number of securities in unrealized loss positions for 12 months or longer | security	954
ABS/CMBS/MBS
Investment Holdings [Line Items]
Unrealized loss	$ 32,065		35,444
Municipal
Investment Holdings [Line Items]
Unrealized loss	$ 84,226		$ 102,725