Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Stock Issued During Period, Shares, New Issues									136,951,452	0	0
Net income	$ 1,610	$ 1,360	$ 726	$ 439	$ 683	$ 528	$ 942	$ 681	$ 4,135	$ 2,834	$ 2,853
Weighted-average shares outstanding									462,519,789	325,589,361	335,609,899
Share-based compensation plans									3,429,610	3,246,017	3,376,388
Adjusted weighted-average shares outstanding and assumed conversions									465,949,399	328,835,378	338,986,287
Basic earnings per share	$ 3.44	$ 2.90	$ 1.55	$ 0.98	$ 2.10	$ 1.63	$ 2.89	$ 2.08	$ 8.94	$ 8.71	$ 8.50
Diluted earnings per share	$ 3.41	$ 2.88	$ 1.54	$ 0.97	$ 2.08	$ 1.62	$ 2.86	$ 2.05	$ 8.87	$ 8.62	$ 8.42
Potential anti-dilutive share conversions									1,206,828	1,601,668	1,024,788