Consolidated Statements of Income and Comprehensive Income (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues
Net premiums earned	$ 201,827	$ 186,367	$ 395,168	$ 363,184
Investment income, net of investment expenses	27,603	29,019	54,365	55,483
Net realized investment gains (includes reclassifications for net unrealized investment gains on available-for-sale securities of $1,606 and $3,088 in 2014; and $4,417 and $5,653 in 2013; previously included in accumulated other comprehensive income (loss))	2,708	4,151	4,902	6,060
Other income	535	182	1,142	297
Total revenues	232,673	219,719	455,577	425,024
Benefits, Losses and Expenses
Losses and loss settlement expenses	142,716	120,435	267,953	217,905
Increase in liability for future policy benefits	8,077	9,869	15,898	18,105
Amortization of deferred policy acquisition costs	40,196	36,708	79,730	74,789
Other underwriting expenses (includes reclassifications for employee benefit costs of $768 and $1,536 in 2014; and $1,243 and $2,485 in 2013; previously included in accumulated other comprehensive income (loss))	20,776	23,308	47,204	45,656
Interest on policyholders’ accounts	7,852	9,081	15,839	18,401
Total benefits, losses and expenses	219,617	199,401	426,624	374,856
Income before income taxes	13,056	20,318	28,953	50,168
Federal income tax expense (includes reclassifications of $293 and $543 in 2014; and $1,111 and $1,109 in 2013; previously included in accumulated other comprehensive income (loss))	2,371	4,822	4,937	12,279
Net income	10,685	15,496	24,016	37,889
Other comprehensive income (loss)
Change in net unrealized appreciation on investments	27,108	(51,782)	51,177	(37,294)
Change in liability for underfunded employee benefit plans	0	0	0	0
Other comprehensive income (loss), before tax and reclassification adjustments	27,108	(51,782)	51,177	(37,294)
Income tax effect	(9,488)	18,115	(17,913)	13,045
Other comprehensive income (loss), after tax, before reclassification adjustments	17,620	(33,667)	33,264	(24,249)
Reclassification adjustment for net realized investment gains included in income	(1,606)	(4,417)	(3,088)	(5,653)
Reclassification adjustment for employee benefit costs included in expense	768	1,243	1,536	2,485
Total reclassification adjustments, before tax	(838)	(3,174)	(1,552)	(3,168)
Income tax effect	293	1,111	543	1,109
Total reclassification adjustments, after tax	(545)	(2,063)	(1,009)	(2,059)
Comprehensive income (loss)	$ 27,760	$ (20,234)	$ 56,271	$ 11,581
Weighted average common shares outstanding (in shares)	25,330,066	25,297,718	25,351,056	25,271,752
Basic earnings per common share (in dollars per share)	$ 0.42	$ 0.61	$ 0.95	$ 1.50
Diluted earnings per common share (in dollars per share)	$ 0.42	$ 0.61	$ 0.94	$ 1.49