Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014		Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 683	$ 528	$ 942	$ 681	[1]	$ 555	$ 785	$ 779	$ 734	$ 2,834	$ 2,853	$ 3,758
Weighted-average shares outstanding										325,589,361	335,609,899	340,906,490
Share-based compensation plans										3,246,017	3,376,388	3,241,085
Adjusted weighted-average shares outstanding and assumed conversions										328,835,378	338,986,287	344,147,575
Basic earnings per share	$ 2.10	$ 1.63	$ 2.89	$ 2.08		$ 1.68	$ 2.35	$ 2.30	$ 2.16	$ 8.71	$ 8.50	$ 11.02
Diluted earnings per share	$ 2.08	$ 1.62	$ 2.86	$ 2.05		$ 1.66	$ 2.32	$ 2.28	$ 2.14	$ 8.62	$ 8.42	$ 10.92
Potential anti-dilutive share conversions										1,601,668	1,024,788	1,031,297

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