Share-Based Compensation - Schedule of Stock Option Activity (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options outstanding, Weighted Average Exercise Price, Beginning Balance	$ 9.26	$ 8.58	$ 11.72
Granted, Weighted Average Exercise Price	$ 27.03	$ 23.35	$ 15.73
Exercised, Weighted Average Exercise Price	$ 7.60	$ 6.31	$ 4.06
Cancelled, Weighted Average Exercise Price	$ 9.49	$ 5.88	$ 7.96
Stock Options outstanding, Weighted Average Exercise Price, Ending Balance	$ 11.56	$ 9.26	$ 8.58
Options exercisable, Weighted Average Exercise Price	$ 9.38
Options outstanding, Weighted Average Remaining Contractual Term	5 years 6 months
Options exercisable, Weighted Average Remaining Contractual Term	4 years 7 months 6 days
Options outstanding, Aggregate Intrinsic Value	$ 767
Options exercisable, Aggregate Intrinsic Value	$ 674
Time Based Stock Options and SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options outstanding, Beginning Balance	21,739,000	24,517,000	25,443,000
Granted, Stock Options	3,174,000	644,000	843,000
Exercised, Stock Options	(5,530,000)	(3,312,000)	(1,598,000)
Cancelled, Stock Options	(192,000)	(110,000)	(171,000)
Stock Options outstanding, Ending Balance	19,191,000	21,739,000	24,517,000
Stock Options exercisable, Ending Balance	14,534,000
Performance Stock Options and SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options outstanding, Beginning Balance	24,573,000	26,009,000	26,474,000
Granted, Stock Options	3,174,000	644,000	121,000
Exercised, Stock Options	(5,128,000)	(1,732,000)	(128,000)
Cancelled, Stock Options	(568,000)	(348,000)	(458,000)
Stock Options outstanding, Ending Balance	22,051,000	24,573,000	26,009,000
Stock Options exercisable, Ending Balance	17,912,000
Total Stock Options and Stock SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options outstanding, Beginning Balance	46,312,000	50,526,000	51,917,000
Granted, Stock Options	6,348,000	1,288,000	964,000
Exercised, Stock Options	(10,658,000)	(5,044,000)	(1,726,000)
Cancelled, Stock Options	(760,000)	(458,000)	(629,000)
Stock Options outstanding, Ending Balance	41,242,000	46,312,000	50,526,000
Stock Options exercisable, Ending Balance	32,446,000