Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement Of Cash Flows [Abstract]
Net cash provided by operating activities	$ 70,946	$ 69,219
Purchase of:
Fixed income securities, available-for-sale	(120,109)	(180,040)
Equity securities	(17,302)	(6,395)
Property and equipment	(1,089)	(1,277)
Other	(2,664)	(1,392)
Proceeds from sale of:
Fixed income securities - available-for-sale	11,819	3,064
Equity securities	15,910	3,501
Equity method investee		14,134
Other	1,350	271
Proceeds from call or maturity of:
Fixed income securities - available-for-sale	71,284	190,303
Net proceeds from sale (purchase) of short-term investments	(12,263)	(79,973)
Net cash used in investing activities	(53,064)	(57,804)
Cash Flows from Financing Activities
Cash dividends paid	(12,337)	(11,839)
Proceeds from stock option exercises	2,588	375
Net cash used in financing activities	(9,749)	(11,464)
Net increase (decrease) in cash	8,133	(49)
Cash at the beginning of the period	36,424	22,818
Cash at March 31	$ 44,557	$ 22,769