Schedule of Details Supporting Computation of Earnings Per Share (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 420	$ 356	$ 893	$ 604
Weighted average outstanding shares of common stock used to compute basic earnings per common share	157,975	162,816	158,446	163,267
Shares used to compute diluted earnings per common share	159,521	164,639	159,962	165,363
Basic earnings per common share	$ 2.66	$ 2.19	$ 5.64	$ 3.70
Diluted earnings per common share	$ 2.63	$ 2.16	$ 5.58	$ 3.65
Number of antidilutive stock options and restricted stock excluded from computation	847	562	1,265	819
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	349	572	367	727
Restricted Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock	1,197	1,251	1,149	1,369