Investments - Investment Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments [Line Items]
Total investment income	$ 241,131	$ 174,326	$ 136,124
Less: investment expense	(6,501)	(5,970)	(6,397)
Net investment income	234,630	168,356	129,727
Fixed maturity securities
Investments [Line Items]
Total investment income	173,167	127,336	100,001
Equity securities
Investments [Line Items]
Total investment income	44,223	43,495	35,064
Short-term investments
Investments [Line Items]
Total investment income	$ 23,741	$ 3,495	$ 1,059