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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 290	$ 368	$ 1,002	$ 1,261
Weighted average outstanding shares of common stock used to compute basic earnings per common share	154,502	157,187	155,006	158,026
Shares used to compute diluted earnings per common share	156,230	158,907	156,641	159,611
Basic earnings per common share (in dollars per share)	$ 1.87	$ 2.34	$ 6.46	$ 7.98
Diluted earnings per common share (in dollars per share)	$ 1.85	$ 2.31	$ 6.39	$ 7.90
Number of antidilutive stock options and restricted stock excluded from computation	43	202	420	910
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	203	289	233	341
Restricted Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock	1,525	1,431	1,402	1,244