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, 2020	Mar. 31, 2019
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	$ 168	$ 37
Gain (loss) on derivative recognized in OCI, net investment hedge	108	20
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative	276	57
Gain (loss) on hedges reclassified to income, cash flow hedge	7	5
Gain (loss) on hedges reclassified to income, net investment hedge	0	0
Amount of Gain or (Loss) Reclassified from Accumulated Other Comprehensive Income into Income	7	5
Interest rate contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	158	10
Interest rate contracts | Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	0	(2)
Foreign exchange contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	10	27
Gain (loss) on derivative recognized in OCI, net investment hedge	108	20
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