Schedule II Condensed Financial Information of Registrant (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows - operating activities
Interest expense paid	$ (13,825)	$ (13,948)	$ (13,515)
Federal income taxes (paid) recovered	(33,672)	(14,444)	(4,130)
Net cash provided by operating activities	205,936	202,848	115,879
Cash flows - investing activities
Net cash provided by (used in) investing activities	(598,326)	(354,798)	(303,007)
Cash flows - financing activities
Dividends paid to shareholders	(32,550)	(22,541)	(18,990)
Exercise of stock options	19,336	5,421	2,127
Net cash used in financing activities	395,398	159,679	188,652
Net increase (decrease) in cash	3,008	7,729	1,524
Cash at beginning of period	15,181	7,452	5,928
Cash at end of period	18,189	15,181	7,452
Parent Company [Member]
Cash flows - operating activities
Interest expense paid	(13,825)	(13,948)	(13,515)
Federal income taxes (paid) recovered	5,996	(118)	12,058
Cash dividends received from subsidiaries	41,000	50,000	26,000
Other, net, including settlement of payables to subsidiaries	(21,235)	7,703	(10,012)
Net cash provided by operating activities	11,936	43,637	14,531
Cash flows - investing activities
Net (increase) decrease in investments	5,488	(10,762)	4,240
Net cash provided by (used in) investing activities	5,488	(10,762)	4,240
Cash flows - financing activities
Dividends paid to shareholders	(32,550)	(22,541)	(18,990)
Acquisition of treasury stock	(3,889)	(15,735)	(2,047)
Exercise of stock options	19,336	5,421	2,127
Net cash used in financing activities	(17,103)	(32,855)	(18,910)
Net increase (decrease) in cash	321	20	(139)
Cash at beginning of period	149	129	268
Cash at end of period	$ 470	$ 149	$ 129