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, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	$ 70	$ 49	$ 61
Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	37	28	31
Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	42	41	40
Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	8	6	4
Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(28)	(19)	(15)
Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	11	(7)	1
Corporate Services Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	90	78	75
Corporate Services Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	38	29	30
Corporate Services Income [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	42	41	40
Corporate Services Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	8	6	4
Corporate Services Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	2	2	1
Corporate Services Income [Member] | Other Credit Derivatives [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)	(1)	(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 Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(1)	(1)	1
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(19)	(28)	(15)
Other Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(1)	(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)	(30)	(21)	(16)
Other Income [Member] | Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	$ 12	$ (6)	$ 0