Earnings (Loss) per Share - Computation of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Basic EPS:
Net income	$ 950	$ 1,704	$ 1,650	$ 2,636
Weighted-average common shares outstanding (in thousands)	563,000	688,727	584,622	692,571
Basic EPS (in dollars per share)	$ 1.69	$ 2.47	$ 2.82	$ 3.81
Diluted EPS:
Net income for purposes of computing diluted EPS	$ 950	$ 1,704	$ 1,650	$ 2,636
Share computation for diluted EPS (in thousands):
Basic weighted average common shares outstanding	563,000	688,727	584,622	692,571
Dilutive effect of stock awards	3,040	18,884	4,142	19,699
Diluted weighted average common shares outstanding	566,040	707,611	588,764	712,270
Diluted EPS (in dollars per share)	$ 1.68	$ 2.41	$ 2.80	$ 3.70
Stock options, stock appreciation rights and restricted stock unit awards excluded because inclusion would be antidilutive	2,601	905	1,845	453