Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	$ 41,529	$ 35,905
Other comprehensive gain (loss) before reclassifications	2	(114)
Amounts reclassified from accumulated other comprehensive loss	183	304
Income taxes	(2)	(20)
Net other comprehensive (loss) income	183	170
Balance	40,010	42,574
Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(2,136)	(2,053)
Other comprehensive gain (loss) before reclassifications	49	(26)
Net other comprehensive (loss) income	49	(26)
Balance	(2,087)	(2,079)
Marketable Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	21
Other comprehensive gain (loss) before reclassifications	(66)	(2)
Net other comprehensive (loss) income	(66)	(2)
Balance	(45)	(2)
Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(19)	(39)
Other comprehensive gain (loss) before reclassifications	19	(86)
Amounts reclassified from accumulated other comprehensive loss	4	109
Net other comprehensive (loss) income	23	23
Balance	4	(16)
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	179	195
Income taxes	(2)	(20)
Net other comprehensive (loss) income	177	175
Balance	(2,332)	(2,291)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(4,643)	(4,558)
Balance	$ (4,460)	$ (4,388)