Financial Instruments - Cash Flow Hedges After-tax Gains/(Losses) (Details) - Cash flow hedges - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains/(losses) recognized in other comprehensive earnings/(losses)	$ (6)	$ (74)	$ (29)	$ (139)
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains/(losses) reclassified from accumulated other comprehensive income into earnings/(losses)	(7)	(12)	(88)	(12)
After-tax gains/(losses) recognized in other comprehensive earnings/(losses)	(5)	(77)	(28)	(142)
Currency exchange contracts | Forecasted transactions
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains/(losses) recognized in other comprehensive earnings/(losses)	$ (1)	$ 3	$ (1)	$ 3