Consolidated Statements of Income and Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Net premiums earned	$ 997,492	$ 936,131	$ 851,695
Investment income, net of investment expenses	51,190	55,284	46,559
Net realized investment gains (includes reclassifications for net unrealized gains on available-for-sale securities of $6,390 in 2017; $4,520 in 2016; and $4,513 in 2015 previously included in accumulated other comprehensive income)	4,055	4,947	1,124
Other income (loss)	0	0	(107)
Total revenues	1,052,737	996,362	899,271
Benefits, losses and expenses
Losses and loss settlement expenses	725,713	652,433	520,087
Amortization of deferred policy acquisition costs	207,746	202,892	180,183
Other underwriting expenses (includes reclassifications for employee benefit costs of $5,408 in 2017; $5,486 in 2016; and $7,468 in 2015 previously included in accumulated other comprehensive income)	103,628	83,540	83,631
Total benefits, losses and expenses	1,037,087	938,865	783,901
Income from continuing operations before income taxes	15,650	57,497	115,370
Federal income tax expense (benefit) (includes reclassifications of ($344) in 2017; $338 in 2016; and $1,034 in 2015 previously included in accumulated other comprehensive income)	(29,220)	8,379	30,050
Net income from continuing operations	44,870	49,118	85,320
Income from discontinued operations, net of taxes	6,153	786	3,806
Net income	51,023	49,904	89,126
Other comprehensive income (loss)
Change in net unrealized appreciation on investments	72,251	13,017	(28,185)
Change in liability for underfunded employee benefit plans	(26,122)	30,045	8,714
Other comprehensive income (loss), before tax and reclassification adjustments	46,129	43,062	(19,471)
Income tax effect	(17,540)	(15,072)	6,814
Other comprehensive income (loss), after tax, before reclassification adjustments	28,589	27,990	(12,657)
Reclassification adjustment for net realized gains included in income	(6,390)	(4,520)	(4,513)
Reclassification adjustment for employee benefit costs included in expense	5,408	5,486	7,468
Total reclassification adjustments, before tax	(982)	966	2,955
Income tax effect	344	(338)	(1,034)
Total reclassification adjustments, after tax	(638)	628	1,921
Comprehensive income	$ 78,974	$ 78,522	$ 78,390
Weighted average common shares outstanding (in shares)	25,103,720	25,335,706	25,047,405
Earnings per common share from continuing operations:
Basic (in dollars per share)	$ 1.79	$ 1.94	$ 3.41
Diluted (in dollars per share)	1.75	1.90	3.38
Earnings per common share:
Basic (in dollars per share)	2.03	1.97	3.56
Diluted (in dollars per share)	$ 1.99	$ 1.93	$ 3.53