Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Statement Of Cash Flows [Abstract]
Net cash provided by operating activities	$ 212,771	$ 243,595
Purchase of:
Fixed income securities, available-for-sale	(369,888)	(365,976)
Equity securities	(45,585)	(25,454)
Property and equipment	(3,840)	(2,790)
Other	(3,591)	(2,669)
Proceeds from sale of:
Fixed income securities - available-for-sale	41,543	19,490
Equity securities	31,473	22,029
Equity method investments		14,134
Other	3,952	473
Proceeds from call or maturity of:
Fixed income securities - available-for-sale	159,869	349,714
Net proceeds from sale (purchase) of short-term investments	9,058	(235,067)
Net cash used in investing activities	(177,009)	(226,116)
Cash Flows from Financing Activities
Cash dividends paid	(25,604)	(24,172)
Proceeds from stock option exercises	3,448	582
Net cash used in financing activities	(22,156)	(23,590)
Net increase (decrease) in cash	13,606	(6,111)
Cash at the beginning of the period	36,424	22,818
Cash at June 30	$ 50,030	$ 16,707