Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	$ 41,529	$ 35,905
Other comprehensive gain (loss) before reclassifications	(40)	(116)
Amounts reclassified from accumulated other comprehensive loss	127	210
Income taxes	(2)	(14)
Net other comprehensive (loss) income	85	80
Balance	39,952	42,979
Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(2,136)	(2,053)
Other comprehensive gain (loss) before reclassifications	(26)	(51)
Net other comprehensive (loss) income	(26)	(51)
Balance	(2,162)	(2,104)
Unrealized Gain/(Loss) on Marketable Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	21
Other comprehensive gain (loss) before reclassifications	(25)	3
Net other comprehensive (loss) income	(25)	3
Balance	(4)	3
Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(19)	(39)
Other comprehensive gain (loss) before reclassifications	11	(68)
Amounts reclassified from accumulated other comprehensive loss	8	80
Net other comprehensive (loss) income	19	12
Balance		(27)
Pension and Other Postretirement Benefit Plans
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(2,509)	(2,466)
Amounts reclassified from accumulated other comprehensive loss	119	130
Income taxes	(2)	(14)
Net other comprehensive (loss) income	117	116
Balance	(2,392)	(2,350)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(4,643)	(4,558)
Balance	$ (4,558)	$ (4,478)