Financial Instruments - Fair Value of Derivative Financial Instruments and Related Notional Amounts (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Asset		$ 1,114	$ 1,140
Liability		577	1,024
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Asset		1,015	1,085
Liability		520	968
Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member]
Derivative [Line Items]
Notional	[1]	18,012	22,984
Asset	[1]	483	654
Liability	[1]	519	586
Designated as Hedging Instrument [Member] | Interest rate contracts [Member]
Derivative [Line Items]
Notional		8,812	11,145
Asset		531	432
Liability		1	383
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member]
Derivative [Line Items]
Notional		16,615	15,154
Asset		99	55
Liability		58	55
Inventory sales [Member] | Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member]
Derivative [Line Items]
Notional	[1]	$ 6,700	$ 5,800

[1] The notional amount of outstanding foreign currency forward-exchange contracts hedging our intercompany forecasted inventory sales was $6.7 billion as of June 30, 2019 and $5.8 billion as of December 31, 2018.