Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 1,231	$ (70)	$ 3,607	$ 2,328
Weighted-average shares outstanding	462,981,973	466,370,784	464,644,013	467,658,334
Share-based compensation plans	3,034,525		3,360,511	3,961,572
Weighted-average shares outstanding and assumed conversions	466,016,498	466,370,784	468,004,524	471,619,906
Basic earnings per share (US$ per share)	$ 2.66	$ (0.15)	$ 7.76	$ 4.98
Diluted earnings per share (US$ per share)	$ 2.64	$ (0.15)	$ 7.71	$ 4.94
Potential anti-dilutive share conversions	3,763,844	2,045,829	3,467,000	1,673,777