Financial Instruments - Cash Flow Hedges After-tax Gains/(Losses) (Details) - Cash Flow Hedges - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains (losses) reclassified from accumulated other comprehensive income into earnings/(losses)	$ (154)	$ 9	$ (27)
After-tax gains (losses) reclassified from accumulated other comprehensive income/(loss)	(199)	(45)	(19)
Commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains (losses) reclassified from accumulated other comprehensive income into earnings/(losses)	0	0	(24)
After-tax gains (losses) reclassified from accumulated other comprehensive income/(loss)	0	0	7
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains (losses) reclassified from accumulated other comprehensive income into earnings/(losses)	(154)	9	0
After-tax gains (losses) reclassified from accumulated other comprehensive income/(loss)	(202)	(45)	12
Forecasted transactions \| Currency exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains (losses) reclassified from accumulated other comprehensive income into earnings/(losses)	0	0	(3)
After-tax gains (losses) reclassified from accumulated other comprehensive income/(loss)	$ 3	$ 0	$ (38)

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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