Derivative Instruments - Summary of Gains (Losses) Recognized in Earnings for Fair Value Hedges, Other Economic Hedges and Customer-Related Positions (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Fair Value Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	$ (6)	$ (31)	$ (2)	$ 63
Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Other Economic Hedges [Member] | Futures and Forwards [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(16)	21	(11)	(34)
Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Other Economic Hedges [Member] | Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	82	102	199	315
Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Other Economic Hedges [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	28	(134)	176	268
Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Other Economic Hedges [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(19)	113	(130)	111
Asset and Liability Management Positions [Member] | Foreign Exchange Forward Contracts [Member] | Commercial Products Revenue [Member] | Other Economic Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(13)	9	(50)	(46)
Asset and Liability Management Positions [Member] | Equity Contracts [Member] | Compensation Expense [Member] | Other Economic Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings		1
Asset and Liability Management Positions [Member] | Credit Contracts [Member] | Other Noninterest Income [Member] | Other Economic Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings		1	1
Asset and Liability Management Positions [Member] | Other Derivatives [Member] | Other Noninterest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings			(1)	(38)
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(18)	(4)	(26)	(3)
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	221	(397)	(352)	1,326
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(190)	417	412	(1,289)
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Futures [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	1	(4)	(1)	3
Customer-Related Positions [Member] | Foreign Exchange Rate Contracts [Member] | Commercial Products Revenue [Member] | Forwards, Spots and Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	23	21	69	61
Customer-Related Positions [Member] | Foreign Exchange Option [Member] | Commercial Products Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	$ 1	$ 1	$ 2	$ 3