Accumulated Other Comprehensive Loss, Excluding Noncontrolling Interests (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	$ 63,407	[1]
Balance, June 30, 2019	59,568	[1]
Foreign currency translation adjustments loss attributable to noncontrolling interests	2
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)	(260)	[2]
Balance, June 30, 2019	(11,535)
Foreign Currency Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	(6,075)
Other comprehensive income/(loss)	(167)	[2]
Balance, June 30, 2019	(6,242)
Derivative Financial Instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	167
Other comprehensive income/(loss)	(200)	[2]
Balance, June 30, 2019	(33)
Cash flow hedge gain to be reclassified within twelve months	153
Available-For-Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	(68)
Other comprehensive income/(loss)	61	[2]
Balance, June 30, 2019	(8)
Actuarial Gains/(Losses) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2018	(6,027)
Other comprehensive income/(loss)	116	[2]
Balance, June 30, 2019	(5,911)
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)	(70)	[2]
Balance, June 30, 2019	$ 658

[1] Amounts may not add due to rounding.

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