Derivatives and Hedging Activities - Pre-Tax Net Gains (Losses) on Derivatives Not Designated as Hedging Instruments (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	$ 17	$ 14	$ 36	$ 41
Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	6	9	20	20
Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	10	9	31	28
Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	1	1	4	3
Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(6)	(5)	(15)	(10)
Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	6	0	(4)	0
Corporate Services Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	16	19	57	54
Corporate Services Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	5	9	21	22
Corporate Services Income [Member] | Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	10	9	31	28
Corporate Services Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	1	1	4	3
Corporate Services Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	1	1
Corporate Services Income [Member] | Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0	0
Consumer Mortgage Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(1)		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)	(1)		0
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	2	(5)	(21)	(13)
Other Income [Member] | Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	1	0	(1)	(2)
Other Income [Member] | Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0	0
Other Income [Member] | Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	0	0	0	0
Other Income [Member] | Credit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	(6)	(5)	(16)	(11)
Other Income [Member] | Other Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total net gains (losses)	$ 7	$ 0	$ (4)	$ 0