Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	$ 37,261	$ 41,529
Other comprehensive gain (loss) before reclassifications	63	52
Amounts reclassified from accumulated other comprehensive loss	52	63
Income taxes		(1)
Net other comprehensive income	115	114
Balance	37,326	41,054
Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(2,139)	(2,136)
Other comprehensive gain (loss) before reclassifications	39	45
Net other comprehensive income	39	45
Balance	(2,100)	(2,091)
Marketable Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	13	21
Other comprehensive gain (loss) before reclassifications	19	(4)
Net other comprehensive income	19	(4)
Balance	32	17
Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	3	(19)
Other comprehensive gain (loss) before reclassifications	5	11
Amounts reclassified from accumulated other comprehensive loss	(3)
Net other comprehensive income	2	11
Balance	5	(8)
Pension and Other Postretirement Benefit Plans
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(2,151)	(2,509)
Amounts reclassified from accumulated other comprehensive loss	55	63
Income taxes		(1)
Net other comprehensive income	55	62
Balance	(2,096)	(2,447)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	(4,274)	(4,643)
Balance	$ (4,159)	$ (4,529)