Schedule II - Condensed Financial Information Of Registrant ( Condensed Statement Of Cash Flows) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Cash provided from operations	$ 942,839	$ 859,464	$ 1,028,593
Cash provided from (used for) investing activities:
Acquisition of investments	(1,433,476)	(1,139,249)	(1,909,014)
Disposition of investments	1,091,959	682,328	970,577
Net decrease (increase) in short-term investments	(73,616)	195,435	128,727
Acquisition of Family Heritage	(186,424)	0	0
Cash provided from (used for) investing activities	(698,039)	(312,133)	(557,641)
Cash provided from (used for) financing activities:
Acquisition of 9 1/4% Senior Notes	0	0	(8,913)
Redemption of 7.1% Junior Subordinated Debentures	(123,711)	0	0
Net issuance (repayment) of commercial paper	245	25,967	(34,432)
Issuance of stock	181,022	162,613	37,863
Acquisitions of treasury stock	(570,165)	(972,556)	(246,006)
Excess tax benefit on stock option exercises	22,602	13,121	3,455
Payment of dividends	(55,527)	(49,125)	(50,061)
Cash provided from (used for) financing activities	(269,112)	(824,485)	(329,621)
Increase (decrease) in cash	(22,403)	(281,566)	133,761
Cash at beginning of year (includes cash of $847 thousand at January 1, 2010 in subsidiary held for sale)	84,113	365,679	231,918
Cash at end of year	61,710	84,113	365,679
3.80% Senior Notes due 2022
Cash provided from (used for) financing activities:
Proceeds from issuance of debt	150,000	0	0
5.875% Junior subordinated debentures due 2052
Cash provided from (used for) financing activities:
Proceeds from issuance of debt	125,000	0	0
Parent Company
Condensed Financial Statements, Captions [Line Items]
Cash provided from (used for) operations before dividends from subsidiaries	(5,652)	(33,042)	(33,403)
Cash dividends from subsidiaries	436,814	769,139	370,947
Cash provided from operations	431,162	736,097	337,544
Cash provided from (used for) investing activities:
Acquisition of investments	0	0	(14,279)
Disposition of investments	3,955	11,828	33
Net decrease (increase) in short-term investments	(17,524)	62,524	106,881
Acquisition of Family Heritage	(213,747)	0	0
Investment in other subsidiaries	(205)	(25,000)	(18,722)
Cash provided from (used for) investing activities	(227,521)	49,352	73,913
Cash provided from (used for) financing activities:
Acquisition of 9 1/4% Senior Notes	0	0	(8,913)
Redemption of 7.1% Junior Subordinated Debentures	(123,711)	0	0
Net issuance (repayment) of commercial paper	245	25,967	(34,432)
Issuance of stock	181,022	162,613	37,863
Acquisitions of treasury stock	(570,165)	(972,556)	(246,006)
Net borrowings to/from subsidiaries	(69,000)	96,000	(86,800)
Excess tax benefit on stock option exercises	12,209	2,021	162
Payment of dividends	(78,797)	(72,395)	(73,331)
Cash provided from (used for) financing activities	(230,740)	(758,350)	(411,457)
Increase (decrease) in cash	(27,099)	27,099	0
Cash at beginning of year (includes cash of $847 thousand at January 1, 2010 in subsidiary held for sale)	27,099	0	0
Cash at end of year	0	27,099	0
Parent Company | 3.80% Senior Notes due 2022
Cash provided from (used for) financing activities:
Proceeds from issuance of debt	296,646	0	0
Parent Company | 5.875% Junior subordinated debentures due 2052
Cash provided from (used for) financing activities:
Proceeds from issuance of debt	$ 120,811	$ 0	$ 0