Share-Based Compensation - Schedule of Stock Option Activity (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options outstanding, Weighted Average Exercise Price, Beginning Balance	$ 15.82	$ 11.56	$ 9.26
Granted, Weighted Average Exercise Price	$ 48.56	$ 37.49	$ 27.03
Exercised, Weighted Average Exercise Price	$ 9.15	$ 8.49	$ 7.60
Cancelled, Weighted Average Exercise Price	$ 29.54	$ 25.50	$ 9.49
Stock Options outstanding, Weighted Average Exercise Price, Ending Balance	$ 21.39	$ 15.82	$ 11.56
Options exercisable, Weighted Average Exercise Price	$ 13.79
Options outstanding, Weighted Average Remaining Contractual Term	5 years 3 months 18 days
Options exercisable, Weighted Average Remaining Contractual Term	3 years 10 months 24 days
Options outstanding, Aggregate Intrinsic Value	$ 1,549
Options exercisable, Aggregate Intrinsic Value	$ 1,186
Time Based Stock Options and SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Outstanding, Beginning Balance	16,809,000	19,191,000	21,739,000
Granted, Stock Options	1,723,000	2,432,000	3,174,000
Exercised, Stock Options	(3,322,000)	(4,498,000)	(5,530,000)
Cancelled, Stock Options	(159,000)	(316,000)	(192,000)
Stock Options Outstanding, Ending Balance	15,051,000	16,809,000	19,191,000
Stock Options Exercisable, Ending Balance	10,102,000
Performance Stock Options and SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Outstanding, Beginning Balance	18,377,000	22,051,000	24,573,000
Granted, Stock Options	1,722,000	2,432,000	3,174,000
Exercised, Stock Options	(5,234,000)	(5,843,000)	(5,128,000)
Cancelled, Stock Options	(121,000)	(263,000)	(568,000)
Stock Options Outstanding, Ending Balance	14,744,000	18,377,000	22,051,000
Stock Options Exercisable, Ending Balance	9,796,000
Total Stock Options and Stock SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Outstanding, Beginning Balance	35,186,000	41,242,000	46,312,000
Granted, Stock Options	3,445,000	4,864,000	6,348,000
Exercised, Stock Options	(8,556,000)	(10,341,000)	(10,658,000)
Cancelled, Stock Options	(280,000)	(579,000)	(760,000)
Stock Options Outstanding, Ending Balance	29,795,000	35,186,000	41,242,000
Stock Options Exercisable, Ending Balance	19,898,000