Investments - Net Investment Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Investment income	$ 171,843	$ 160,598	$ 159,608
Investment expenses	(4,367)	(4,160)	(5,212)
Investment income, net of expenses	167,476	156,438	154,396
Total fixed income securities
Schedule of Investments [Line Items]
Investment income	166,306	160,030	157,065
Equity securities
Schedule of Investments [Line Items]
Investment income	437	471	620
Cash equivalents
Schedule of Investments [Line Items]
Investment income	5,049	75	1,648
Other
Schedule of Investments [Line Items]
Investment income	$ 51	$ 22	$ 275