Accumulated Other Comprehensive Loss, Excluding Noncontrolling Interests (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2017	[1]	$ 71,308
Balance, September 30, 2018	[1]	71,319
Foreign currency translation adjustments loss attributable to noncontrolling interests		20
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2017		(9,321)
Other comprehensive income/(loss) due to the adoption of new accounting standards	[2]		$ (913)
Other comprehensive income/(loss)	[3]	(183)
Balance, September 30, 2018		(10,417)
Foreign Currency Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2017		(5,180)
Other comprehensive income/(loss)	[3]	(589)
Balance, September 30, 2018		(5,772)
Derivative Financial Instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2017		(30)
Other comprehensive income/(loss)	[3]	279
Balance, September 30, 2018		248
Cash flow hedge gain to be reclassified within twelve months		177
Available-For-Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2017		401
Other comprehensive income/(loss)	[3]	(116)
Balance, September 30, 2018		(131)
Actuarial Gains/(Losses) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2017		(5,262)
Other comprehensive income/(loss)	[3]	361
Balance, September 30, 2018		(5,538)
Prior Service (Costs)/Credits and Other [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, December 31, 2017		750
Other comprehensive income/(loss)	[3]	(118)
Balance, September 30, 2018		$ 776
ASU 2018-02 [Member] | Derivative Financial Instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income/(loss) due to the adoption of new accounting standards	[2]		(1)
ASU 2018-02 [Member] | Actuarial Gains/(Losses) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income/(loss) due to the adoption of new accounting standards	[2]		(637)
ASU 2018-02 [Member] | Prior Service (Costs)/Credits and Other [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income/(loss) due to the adoption of new accounting standards	[2]		144
ASU 2016-01 [Member] | Foreign Currency Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income/(loss) due to the adoption of new accounting standards	[2]		(2)
ASU 2016-01 [Member] | Available-For-Sale Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income/(loss) due to the adoption of new accounting standards	[2]		$ (416)

[1] Amounts may not add due to rounding.

[2] Amounts represent the cumulative effect adjustments as of January 1, 2018 from the adoption of new accounting standards related to (i) financial assets and liabilities and (ii) the reclassification of certain tax effects from AOCI. For additional information, see Note 1B.

[3] Amounts do not include foreign currency translation adjustments attributable to noncontrolling interests of $20 million loss for the first nine months of 2018.