Schedule II - Condensed Financial Information of Registrant (Balance Sheets (Parent Company)) (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Assets:
Cash and cash equivalents	$ 911,742,000	$ 642,952,000	$ 515,430,000	$ 1,134,835,000
Fixed maturity securities available for sale at fair value (cost $244,921 and $244,804 at December 31, 2011 and 2010, respectively)	11,312,037,000	11,209,154,000
Equity securities available for sale	443,439,000	561,053,000
Deferred Federal income taxes	433,062,000	391,407,000
Current Federal income taxes	9,670,000	23,605,000
Property, furniture and equipment at cost, less accumulated depreciation	262,275,000	254,720,000
Other assets	192,729,000	198,963,000
Total assets	18,487,731,000	17,528,547,000
Liabilities:
Other liabilities	866,229,000	836,001,000
Deferred Federal income taxes	464,685,000	325,915,000
Junior subordinated debentures	242,997,000	242,784,000
Senior notes	1,500,503,000	1,500,419,000
Total liabilities	14,471,779,000	13,818,691,000
Stockholders' equity:
Preferred stock	0	0
Common stock	47,024,000	47,024,000
Additional paid-in capital	941,109,000	935,099,000
Retained earnings (including accumulated undistributed net income of subsidiaries of $3,384,149 and $3,309,411 at December 31, 2011 and 2010, respectively)	4,546,232,000	4,194,684,000
Accumulated other comprehensive income	354,851,000	276,563,000
Treasury stock, at cost	(1,880,790,000)	(1,750,494,000)
Total stockholders' equity	4,015,952,000	3,709,856,000
Total liabilities and stockholders' equity	18,487,731,000	17,528,547,000
Equity securities available for sale at cost $0 in 2011 and 2010	342,393,000	404,235,000
Parent Company [Member]
Assets:
Cash and cash equivalents	270,637,000	29,476,000	117,648,000	131,423,000
Fixed maturity securities available for sale at fair value (cost $244,921 and $244,804 at December 31, 2011 and 2010, respectively)	247,537,000	246,275,000
Equity securities available for sale	81,811,000	109,748,000
Investment in subsidiaries	5,389,531,000	5,261,686,000
Deferred Federal income taxes	0	80,861,000
Current Federal income taxes	15,137,000	19,163,000
Property, furniture and equipment at cost, less accumulated depreciation	6,595,000	6,431,000
Other assets	6,951,000	7,969,000
Total assets	6,018,199,000	5,761,609,000
Liabilities:
Due to subsidiaries	141,492,000	189,499,000
Other liabilities	146,823,000	161,666,000
Deferred Federal income taxes	12,283,000	0
Junior subordinated debentures	242,997,000	242,784,000
Senior notes	1,466,178,000	1,464,784,000
Total liabilities	2,009,773,000	2,058,733,000
Stockholders' equity:
Preferred stock	0	0
Common stock	47,024,000	47,024,000
Additional paid-in capital	941,109,000	935,099,000
Retained earnings (including accumulated undistributed net income of subsidiaries of $3,384,149 and $3,309,411 at December 31, 2011 and 2010, respectively)	4,546,232,000	4,194,684,000
Accumulated other comprehensive income	354,851,000	276,563,000
Treasury stock, at cost	(1,880,790,000)	(1,750,494,000)
Total stockholders' equity	4,008,426,000	3,702,876,000
Total liabilities and stockholders' equity	6,018,199,000	5,761,609,000
Fixed maturity securities available for sale at cost: $244,921 and $244,804 in 2011 and 2010, respectively	244,921	244,804
Equity securities available for sale at cost $0 in 2011 and 2010	0	0
Accumulated undistributed net income of subsidiaries of $3,384,149 and $3,309,411 in 2011 and 2010, respectively	$ 3,384,149	$ 3,309,411