Schedule of Details Supporting Computation of Earnings Per Share (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 368	$ 426	$ 1,261	$ 1,030
Weighted average outstanding shares of common stock used to compute basic earnings per common share	157,187	160,639	158,026	162,391
Shares used to compute diluted earnings per common share	158,907	162,418	159,611	164,382
Basic earnings per common share	$ 2.34	$ 2.65	$ 7.98	$ 6.34
Diluted earnings per common share	$ 2.31	$ 2.62	$ 7.90	$ 6.27
Number of antidilutive stock options and restricted stock excluded from computation	202	758	910	799
Employee Stock Options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock	289	431	341	629
Restricted Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock	1,431	1,348	1,244	1,362