Earnings per Share - Computation of Basic and Diluted Earnings per Share (EPS) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic EPS:
Net income	$ 1,704	$ 864	$ 2,636	$ 1,343
Weighted-average common shares outstanding	688,727	720,600	692,571	722,286
Basic EPS	$ 2.47	$ 1.20	$ 3.81	$ 1.86
Diluted EPS:
Net income	$ 1,704	$ 864	$ 2,636	$ 1,343
Change in fair value of conversion feature on 7.25% convertible senior notes		(2)		3
Net income for purposes of computing diluted EPS	$ 1,704	$ 862	$ 2,636	$ 1,346
Share computation for diluted earnings per share (in thousands):
Weighted-average shares outstanding	688,727	720,600	692,571	722,286
Dilutive effect of stock awards	18,884	14,167	19,699	13,850
Assumed conversion of convertible senior notes				1,915
Weighted average common shares outstanding	707,611	734,767	712,270	738,051
Diluted EPS	$ 2.41	$ 1.17	$ 3.70	$ 1.82
Stock options, SARs and RSUs because inclusion would be antidilutive	905	582	453	307