Shareholders' Equity - Additional Information (Detail) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Equity [Abstract]
Stock acquired, shares	5.5	7.5	18.9
Share repurchases under stock repurchase program, amount	$ 360,000,000	$ 360,000,000	$ 788,000,000
Shares repurchased for dilution purposes, shares	1.9	4.3	4.4
Shares repurchased for dilution purposes, amount	122,000,000	210,000,000	185,000,000
Retirement of treasury stock	5.0	6.5	7.5
Dividends paid by subsidiaries to parent company	488,376,000	436,814,000	769,139,000
Proceeds from Sale of United Investors			305,000,000
Maximum amount of dividends expected to be available from subsidiaries without regulatory approval during 2014	451,000,000
Restricted net assets	878,000,000
Dividend	471,000,000
Retained earnings restricted by lenders' covenants	3,180,000,000
Retained earnings	$ 3,545,939,000	$ 3,403,338,000
Anti-dilutive shares	0	0	3.5