Derivatives and Hedging Activities - Derivative Instrument Cash Flow Hedge Earning Recognized by Income Statement Location (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	$ 71	$ 266	$ 598	$ 372
Net Gains (Losses) Reclassified From OCI Into Income	89	(19)	122	(44)
Interest income – loans | Interest rate | Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	62	270	624	385
Net Gains (Losses) Reclassified From OCI Into Income	90	(19)	124	(43)
Interest expense — Long-term debt | Interest rate | Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	(1)	(2)	(6)	(3)
Net Gains (Losses) Reclassified From OCI Into Income	(1)	0	(2)	(1)
Investment banking and debt placement fees | Interest rate | Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI	10	(1)	(20)	(6)
Net Gains (Losses) Reclassified From OCI Into Income	$ 0	0	0	0
Other income | Foreign exchange | Net Investment Hedges
Derivatives, Fair Value [Line Items]
Net Gains (Losses) Recognized in OCI		(1)	0	(4)
Net Gains (Losses) Reclassified From OCI Into Income		$ 0	$ 0	$ 0