Consolidated Statements of Income and Comprehensive Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Revenues
Net premiums earned	$ 828,330		$ 754,846		$ 694,994
Investment income, net of investment expenses	104,609		112,799		111,905
Net realized investment gains (losses)
Other-than-temporary impairment charges	0		(139)		(4)
All other net realized gains (includes reclassifications for net unrealized gains on available-for-sale securities of $5,805 in 2014; $6,812 in 2013; and $4,102 in 2012 previously included in accumulated other comprehensive income)	7,270		8,834		5,457
Total net realized investment gains	7,270		8,695		5,453
Other income	1,685		702		891
Total revenues	941,894		877,042		813,243
Benefits, losses and expenses
Losses and loss settlement expenses	536,243		458,814		459,706
Increase in liability for future policy benefits	36,623		37,625		43,095
Amortization of deferred policy acquisition costs	167,449		153,677		141,834
Other underwriting expenses (includes reclassifications for employee benefit costs of $3,072 in 2014; $5,868 in 2013; and $4,971 in 2012 previously included in accumulated other comprehensive income)	94,871		89,861		81,125
Interest on policyholders' accounts	30,245		35,163		41,409
Total benefits, losses and expenses	865,431		775,140		767,169
Income before income taxes	76,463		101,902		46,074
Federal income tax expense (includes reclassifications of ($704) in 2014; ($331) in 2013; and $304 in 2012 previously included in accumulated other comprehensive income)	17,326		25,762		5,862
Net income	59,137		76,140		40,212
Other comprehensive income (loss)
Change in net unrealized appreciation on investments	55,888		(35,489)		34,436
Change in liability for underfunded employee benefit plans	(47,685)		24,066		(15,922)
Other comprehensive income (loss), before tax and reclassification adjustments	8,203		(11,423)		18,514
Income tax effect	(2,871)		3,998		(6,477)
Other comprehensive income (loss), after tax, before reclassification adjustments	5,332		(7,425)		12,037
Reclassifications for unrealized net gains on available-for-sale securities	(5,085)		(6,812)		(4,102)
Reclassification adjustment for employee benefit costs included in expense	3,072		5,868		4,971
Total reclassification adjustments, before tax	(2,013)		(944)		869
Income tax effect	704		331		(304)
Total reclassification adjustments, after tax	(1,309)		(613)		565
Comprehensive income	$ 63,160		$ 68,102		$ 52,814
Weighted average common shares outstanding (in shares)	25,230,854		25,325,695		25,447,918
Basic earnings per common share (in usd per share)	$ 2.34	[1]	$ 3.01	[1]	$ 1.58
Diluted earnings per common share (in usd per share)	$ 2.32	[1]	$ 2.98	[1]	$ 1.58

[1] The sum of the quarterly reported amounts may not equal the full year, as each is computed independently.