Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income	$ (70)	$ 1,360	$ 2,328	$ 2,525
Weighted-average shares outstanding	466,370,784	468,021,093	467,658,334	460,631,794
Share-based compensation plans	3,820,673	3,375,269	3,961,572	3,439,017
Weighted-average shares outstanding and assumed conversions	466,370,784	471,396,362	471,619,906	464,070,811
Basic earnings per share (US$ per share)	$ (0.15)	$ 2.90	$ 4.98	$ 5.48
Diluted earnings per share (US$ per share)	$ (0.15)	$ 2.88	$ 4.94	$ 5.44
Potential anti-dilutive share conversions	2,045,829	1,306,710	1,673,777	1,635,337