Derivative Instruments - Impact on Statements of Income, Cash Flow Hedges (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivatives gains/(losses) recorded in income and other comprehensive income/(loss)
Recognition of net losses related to cash flow hedges in Income	$ (74)
Maximum length of time hedged in forecasted transactions, terminated cash flow hedges	6 years
Maximum length of time hedged in forecasted transactions, open cash flow hedges	6 years
Cash Flow Hedging
Derivatives gains/(losses) recorded in income and other comprehensive income/(loss)
Amounts reclassified from AOCI to income	$ 18
Amounts recorded in OCI	(245)
Total change in OCI for period	(263)
Amounts reclassified from AOCI to income		$ (134)	$ (360)
Amounts recorded in OCI		147	(450)
Total change in OCI for period		281	(90)
Cash Flow Hedging \| Interest rate
Derivatives gains/(losses) recorded in income and other comprehensive income/(loss)
Amounts reclassified from AOCI to income	44
Amounts recorded in OCI	(44)
Total change in OCI for period	(88)
Amounts reclassified from AOCI to income		(17)	(74)
Amounts recorded in OCI		12	(55)
Total change in OCI for period		29	19
Cash Flow Hedging \| Foreign exchange
Derivatives gains/(losses) recorded in income and other comprehensive income/(loss)
Amounts reclassified from AOCI to income	(26)
Amounts recorded in OCI	(201)
Total change in OCI for period	$ (175)
Amounts reclassified from AOCI to income		(117)	(286)
Amounts recorded in OCI		135	(395)
Total change in OCI for period		$ 252	$ (109)

Cash flow hedge gains and losses.

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For an open cash flow hedge, maximum length of time over which the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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For a terminated cash flow hedge, maximum length of time over which the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

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-Publisher FASB
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- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

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- Definition

Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

+ References

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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

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- Definition

Amount, before 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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Amount before tax, after reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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