Derivatives and Hedging Activities - Pre-Tax Net Gains (Losses) on Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	$ 55	$ 70	$ 49
Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	44	37	28
Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	45	42	41
Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	6	8	6
Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(42)	(28)	(19)
Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	2	11	(7)
Corporate Services Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	91	90	78
Corporate Services Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	46	38	29
Corporate Services Income [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	45	42	41
Corporate Services Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	6	8	6
Corporate Services Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(6)	2	2
Corporate Services Income [Member] | Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0
Consumer Mortgage Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	2	(1)	(1)
Consumer Mortgage Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0
Consumer Mortgage Income [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0
Consumer Mortgage Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0
Consumer Mortgage Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0
Consumer Mortgage Income [Member] | Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	2	(1)	(1)
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(38)	(19)	(28)
Other Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(2)	(1)	(1)
Other Income [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0
Other Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0
Other Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(36)	(30)	(21)
Other Income [Member] | Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	$ 0	$ 12	$ (6)