Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Statement Of Cash Flows [Abstract]
Net cash provided by operating activities	$ 243,595	$ 170,645
Purchase of:
Fixed income securities, available-for-sale	(365,976)	(292,056)
Equity securities	(25,454)	(36,605)
Property and equipment	(2,790)	(3,024)
Other	(2,669)	(6,326)
Proceeds from sale of:
Fixed income securities - available-for-sale	19,490	20,892
Equity securities	22,029	53,525
Equity method investments	14,134
Other	473	1,172
Proceeds from call or maturity of:
Fixed income securities - available-for-sale	349,714	137,476
Net proceeds from sale (purchase) of short-term investments	(235,067)
Net cash used in investing activities	(226,116)	(124,946)
Cash Flows from Financing Activities
Cash dividends paid	(24,172)	(23,115)
Proceeds from stock option exercises	582	1,656
Net cash used in financing activities	(23,590)	(21,459)
Net increase in cash	(6,111)	24,240
Cash at the beginning of the period	22,818	88,804
Cash at June 30	$ 16,707	$ 113,044