Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Net premiums earned	$ 346,156	$ 368,704	$ 375,894
Net investment income	29,281	28,106	27,902
Net realized losses on investments	(647)	(494)	(2,494)
Loss on disposal of assets	(2)	(1)	(664)
Fee and other income	420	347	316
Total revenues	375,208	396,662	400,954
Expenses
Loss and loss adjustment expenses incurred	209,324	199,031	214,573
Underwriting and certain other operating costs	28,333	29,470	32,162
Commissions	24,812	26,243	27,509
Salaries and benefits	25,631	24,881	24,442
Policyholder dividends	4,868	4,216	1,301
Total expenses	292,968	283,841	299,987
Income before income taxes	82,240	112,821	100,967
Income tax expense	36,009	34,956	30,505
Net income	46,231	77,865	70,462
Net income available to common shareholders	$ 46,231	$ 77,865	$ 70,462
Earnings per share
Basic	$ 2.41	$ 4.08	$ 3.72
Diluted	$ 2.40	$ 4.05	$ 3.69
Shares used in computing earnings per share
Basic	19,165,489	19,105,806	18,941,077
Diluted	19,245,866	19,203,650	19,119,186
Extraordinary cash dividends declared per common share	$ 3.50	$ 3.25	$ 3.00
Cash dividends declared per common share	$ 0.80	$ 0.72	$ 0.60