Condensed Consolidated Statements of Earnings and Comprehensive Earnings - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Net premiums earned	$ 241,000	$ 208,734	$ 469,595	$ 424,316
Net investment income	16,661	16,917	33,085	34,695
Net realized gains (losses)	36,463	(2,109)	50,613	13,043
Net unrealized gains (losses) on equity securities	3,956	74,705	32,118	(55,690)
Consolidated revenue	298,080	298,247	585,411	416,364
Losses and settlement expenses	107,026	101,202	211,918	212,223
Policy acquisition costs	77,235	69,463	152,225	142,404
Insurance operating expenses	20,148	13,906	38,944	28,287
Interest expense on debt	1,904	1,903	3,805	3,800
General corporate expenses	3,686	1,994	7,028	3,749
Total expenses	209,999	188,468	413,920	390,463
Equity in earnings of unconsolidated investees	13,940	5,100	20,364	9,614
Earnings before income taxes	102,021	114,879	191,855	35,515
Income tax expense	20,206	22,713	37,028	4,616
Net earnings	81,815	92,166	154,827	30,899
Other comprehensive earnings (loss), net of tax	15,177	53,571	(29,570)	40,540
Comprehensive earnings	$ 96,992	$ 145,737	$ 125,257	$ 71,439
Basic net earnings per share	$ 1.81	$ 2.05	$ 3.43	$ 0.69
Diluted net earnings per share	$ 1.79	$ 2.04	$ 3.39	$ 0.68
Weighted average number of common shares outstanding:
Basic	45,226	44,951	45,202	44,936
Diluted	45,715	45,274	45,703	45,311