Accumulated Other Comprehensive Loss, Excluding Noncontrolling Interests (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	$ 63,407	[1]
Balance, March 31, 2019	58,806	[1]
Foreign currency translation adjustments loss attributable to noncontrolling interests	4
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	(11,275)
Other comprehensive income/(loss)	353	[2]
Balance, March 31, 2019	(10,923)
Foreign Currency Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	(6,075)
Other comprehensive income/(loss)	304	[2]
Balance, March 31, 2019	(5,772)
Derivative Financial Instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	167
Other comprehensive income/(loss)	0	[2]
Balance, March 31, 2019	167
Cash flow hedge gain to be reclassified within twelve months	345
Available-For-Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	(68)
Other comprehensive income/(loss)	44	[2]
Balance, March 31, 2019	(24)
Actuarial Gains/(Losses) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	(6,027)
Other comprehensive income/(loss)	40	[2]
Balance, March 31, 2019	(5,986)
Prior Service (Costs)/Credits and Other [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	728
Other comprehensive income/(loss)	(35)	[2]
Balance, March 31, 2019	$ 693

[1] Amounts may not add due to rounding.

[2] Amounts do not include foreign currency translation adjustments attributable to noncontrolling interests of $4 million loss for the first three months of 2019.