Derivatives and Hedging Activities - Pre-Tax Net Gains (Losses) on Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	$ 12	$ 18
Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	6	11
Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	10	11
Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	1	3
Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(6)	(3)
Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	1	(4)
Corporate Services Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	20	25
Corporate Services Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	8	9
Corporate Services Income [Member] | Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	10	11
Corporate Services Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	1	3
Corporate Services Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	1	2
Corporate Services Income [Member] | Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Consumer Mortgage Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Consumer Mortgage Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Consumer Mortgage Income [Member] | Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Consumer Mortgage Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Consumer Mortgage Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Consumer Mortgage Income [Member] | Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(8)	(7)
Other Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(2)	2
Other Income [Member] | Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Other Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0
Other Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(7)	(5)
Other Income [Member] | Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	$ 1	$ (4)