Derivative Instruments - Summary of Gains (Losses) Recognized in Earnings for Other Economic Hedges and Customer-Related Positions (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
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		$ (6)
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	$ (1,164)	(250)
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	1,167	269
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	8	(2)
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	22
Customer-Related Positions [Member] | Foreign Exchange Option [Member] | Commercial Products Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings		1
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Futures and Forwards [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	58	6
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	42	40
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(79)	31
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(31)	(40)
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Foreign Exchange Forward Contracts [Member] | Other Noninterest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	12	(7)
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Equity Contracts [Member] | Compensation Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	$ (1)	1
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Credit Contracts [Member] | Other Noninterest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings		$ 1