Derivative Financial Instruments - Schedule of Differences Between the Gains (Losses) on the Derivative and The Gains (Losses) on the Hedged Item (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	$ 37	$ (108)
Gain (loss) on derivative recognized in OCI, net investment hedge	20	(36)
Gain (loss) on hedges reclassified to income, cash flow hedge	5	8
Gain (loss) on hedges reclassified to income, net investment hedge	0	0
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative	57	(144)
Amount of Gain or (Loss) Reclassified from Accumulated Other Comprehensive Income into Income	5	8
Interest rate contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	10	(20)
Interest rate contracts \| Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	(2)	1
Foreign exchange contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	27	(88)
Gain (loss) on derivative recognized in OCI, net investment hedge	20	(36)
Foreign exchange contracts \| Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	7	7
Foreign exchange contracts \| Gains (Losses) related to investment securities, net
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, net investment hedge	$ 0	$ 0

Other Comprehensive Income (Loss), Derivative, Before Reclassification And Tax

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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 20
-Section 45
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Amount, before tax, of reclassification from accumulated other comprehensive income (AOCI) for gain (loss) from derivative designated and qualifying as net investment hedge.

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