Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	$ 41,529	$ 35,905
Other comprehensive gain (loss) before reclassifications	52	(65)
Amounts reclassified from accumulated other comprehensive loss	63	164
Income taxes	(1)	(7)
Net other comprehensive (loss) income	114	92
Balance	41,054	35,662
Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(2,136)	(2,053)
Other comprehensive gain (loss) before reclassifications	45	17
Net other comprehensive (loss) income	45	17
Balance	(2,091)	(2,036)
Unrealized Gain/(Loss) on Marketable Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	21
Other comprehensive gain (loss) before reclassifications	(4)	3
Net other comprehensive (loss) income	(4)	3
Balance	17	3
Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(19)	(39)
Other comprehensive gain (loss) before reclassifications	11	(85)
Amounts reclassified from accumulated other comprehensive loss		94
Net other comprehensive (loss) income	11	9
Balance	(8)	(30)
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	63	70
Income taxes	(1)	(7)
Net other comprehensive (loss) income	62	63
Balance	(2,447)	(2,403)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(4,643)	(4,558)
Balance	$ (4,529)	$ (4,466)