Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Statement Of Cash Flows [Abstract]
Net cash provided by operating activities	$ 103,514	$ 70,946
Purchase of:
Fixed income securities, available-for-sale	(153,952)	(120,109)
Equity securities	(41,503)	(17,302)
Property and equipment	(1,053)	(1,089)
Other	(2,710)	(2,664)
Proceeds from sale of:
Fixed income securities - available-for-sale	10,207	11,819
Equity securities	26,679	15,910
Other	953	1,350
Proceeds from call or maturity of:
Fixed income securities - available-for-sale	99,651	71,284
Net proceeds from sale (purchase) of short-term investments	(41,686)	(12,263)
Net cash used in investing activities	(103,414)	(53,064)
Cash Flows from Financing Activities
Cash dividends paid	(13,761)	(12,337)
Proceeds from stock option exercises	929	2,588
Net cash used in financing activities	(12,832)	(9,749)
Net increase (decrease) in cash	(12,732)	8,133
Cash at the beginning of period	39,790	36,424
Cash at March 31,	$ 27,058	$ 44,557