Debt - Additional Information (Detail) (USD $)			12 Months Ended	1 Months Ended			12 Months Ended	1 Months Ended			12 Months Ended	1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012 Family Heritage [Member]	Oct. 24, 2012 7.1% Trust Preferred Securities [Member]	Oct. 24, 2012 Junior Subordinated Debentures Due 6/1/46 [Member]	Sep. 24, 2012 Senior Notes, Due 9/15/22 [Member]	Dec. 31, 2013 Senior Notes, Due 9/15/22 [Member]	Aug. 01, 2013 7.375% Notes [Member]	Sep. 24, 2012 7.375% Notes [Member]	Sep. 24, 2012 Junior Subordinated Debentures Due 12/15/52 [Member]	Dec. 31, 2013 Junior Subordinated Debentures Due 12/15/52 [Member]	Sep. 24, 2012 Insurance Subsidiary [Member] Senior Notes, Due 9/15/22 [Member]
Debt Instrument [Line Items]
Debt issued, par amount	$ 1,232,399,000					$ 300,000,000	$ 150,000,000			$ 125,000,000	$ 125,000,000	$ 150,000,000
Periodic Interest Payments Due						Semi-annually	3/15 & 9/15			Quarterly	quarterly
Interest rate					7.10%	3.80%	3.80%	7.375%		5.875%	5.875%
Commencement date for interest payable						Mar. 15, 2013				Dec. 15, 2012
Proceeds from issuance of debt						297,000,000				121,000,000		147,000,000
Debt instrument spread						0.0030
Remaining proceeds to repay principal amount					124,000,000			94,000,000
Debt instrument, maturity date			Mar. 15, 2036				Sep. 15, 2022		Aug. 01, 2013		Dec. 15, 2052
Issuance Cost										4,200,000
Redemption Period					40 years					40 years
Preferred Securities redeemed				120,000,000
Redemption of preferred securities and accrued dividend				121,000,000
After tax expected loss on repurchase				2,700,000
Debt assumed			20,000,000
Debt instrument, Fair Value	1,360,461,000		20,000,000				145,178,000				108,450,000
Debt instrument, amortized cost	$ 990,865,000	$ 989,686,000	$ 20,000,000
Debt instrument, basis spread			3.30%