Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Net earned premiums	$ 788,777	$ 781,587	$ 774,420
Net investment income	46,665	43,788	38,758
Earnings from partnership investments	1,937	6,915	2,082
Net realized gains on investments	2,976	3,226	6,036
Change in unrealized gains on equity investments	21,454	(16,324)
Net impairment losses on investments (a)	(889)	(228)	(256)
Finance and other service income	16,833	17,533	18,073
Total revenue	877,753	836,497	839,113
Expenses
Losses and loss adjustment expenses	509,846	485,513	503,887
Underwriting, operating and related expenses	244,136	246,643	248,436
Interest expense	90	90	90
Total expenses	754,072	732,246	752,413
Income before income taxes	123,681	104,251	86,700
Income tax expense	24,080	21,056	24,313
Net income	$ 99,601	$ 83,195	$ 62,387
Earnings per weighted average common share:
Basic (in dollars per share)	$ 6.52	$ 5.48	$ 4.13
Diluted (in dollars per share)	6.46	5.43	4.10
Cash dividends paid per common share (in dollars per share)	$ 3.40	$ 3.20	$ 3.00
Number of shares used in computing earnings per share:
Basic (in shares)	15,201,132	15,080,269	15,010,751
Diluted (in shares)	15,337,807	15,229,898	15,135,348