Investments - Disposition of Fixed Income and Equity Securities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Summary of the disposition of fixed income and equity securities
Fixed income securities - available-for-sale	$ 26,158	$ 46,448
Fixed income securities - available-for-sale	414,529	176,616
Net Realized Gain (Loss) - Fixed income securities - available-for-sale	(2,000)
SALES
Summary of the disposition of fixed income and equity securities
Fixed income securities - available-for-sale	25,983	48,559
Gross Realized Gains - Fixed income securities - available-for-sale	145	286
Gross Realized Losses - Fixed income securities - available-for-sale	(1,035)	(2,481)
Net Realized Gain (Loss) - Fixed income securities - available-for-sale	(890)	(2,195)
Proceeds from Sales - Equity securities	36,708	59,264
Gross Realized Gains - Equity securities	15,990	20,410
Gross Realized Losses - Equity securities	(101)	(609)
Net Realized Gain (Loss) - Equity securities	15,889	19,801
Calls And Maturities Of Marketable Securities
Summary of the disposition of fixed income and equity securities
Fixed income securities - available-for-sale	434,263	176,991
Gross Realized Gains - Fixed income securities - available-for-sale	38	142
Gross Realized Losses - Fixed income securities - available-for-sale	(236)	(55)
Net Realized Gain (Loss) - Fixed income securities - available-for-sale	$ (198)	$ 87