Shareholders' Equity - Additional Information (Detail) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Stockholders Equity [Line Items]
Stock acquired, shares	7.5	18.9	5.7
Share repurchases under stock repurchase program, amount	$ 360,000,000	$ 788,000,000	$ 204,000,000
Shares repurchased for dilution purposes, shares	4.3	4.4	1.1
Shares repurchased for dilution purposes, amount	210,000,000	185,000,000	42,000,000
Retirement of treasury stock	6.5	7.5	6.0
Dividends paid by subsidiaries to parent company	437,000,000
Maximum amount of dividends expected to be available from subsidiaries without regulatory approval during 2012	428,000,000
Restricted net assets	930,000,000
Dividend	506,000,000
Retained earnings restricted by lenders' covenants	3,230,000,000
Retained earnings	$ 3,403,338,000	$ 3,264,711,000
Anti-dilutive shares	0	3.5	10.3