Financial Instruments (Derivative Notional Amounts) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Foreign exchange contracts | Fair Value of Derivatives Not Designated as Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional principal	$ 39,861	$ 43,497
Foreign exchange contracts | Cash flow hedges | Fair Value of Derivatives Designated as Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional principal	10,187	13,207
Foreign exchange contracts | Fair value hedges | Fair Value of Derivatives Designated as Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional principal	1,569	455
Foreign exchange contracts | Net investment hedges | Fair Value of Derivatives Designated as Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional principal	9,965	9,318
Other contracts | Fair Value of Derivatives Not Designated as Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional principal	$ 2,399	$ 117