Consolidated Statements of Earnings and Comprehensive Earnings - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Consolidated Statements of Earnings and Comprehensive Earnings
Net premiums earned	$ 737,937	$ 728,608	$ 700,161
Net investment income	54,876	53,075	54,644
Net realized gains	6,970	34,740	39,829
Other-than-temporary-impairment (OTTI) losses on investments	(2,559)	(95)	0
Consolidated revenue	797,224	816,328	794,634
Losses and settlement expenses	401,584	349,778	299,045
Policy acquisition costs	252,515	249,612	241,078
Insurance operating expenses	56,994	53,093	51,480
Interest expense on debt	7,426	7,426	7,426
General corporate expenses	11,340	10,170	9,837
Total expenses	729,859	670,079	608,866
Equity in earnings of unconsolidated investees	17,224	10,833	10,914
Earnings (loss) before income taxes	84,589	157,082	196,682
Income tax expense:
Current	9,302	41,034	52,104
Deferred	(29,741)	1,128	7,034
Total tax expense (benefit)	(20,439)	42,162	59,138
Net earnings	105,028	114,920	137,544
Other comprehensive earnings (loss), net of tax	35,309	(1,164)	(47,609)
Comprehensive earnings	$ 140,337	$ 113,756	$ 89,935
Basic:
Net earnings per share (in dollars per share)	$ 2.39	$ 2.63	$ 3.18
Comprehensive earnings per share (in dollars per share)	3.19	2.60	2.08
Diluted:
Net earnings per share (in dollars per share)	2.36	2.59	3.12
Comprehensive earnings per share (in dollars per share)	$ 3.15	$ 2.56	$ 2.04
Weighted average number of common shares outstanding
Basic (in shares)	44,033	43,772	43,299
Diluted (in shares)	44,500	44,432	44,131