Derivative Instruments - Summary of Gains (Losses) Recognized in Earnings for Other Economic Hedges and Customer-Related Positions (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Commercial Products Revenue [Member] | Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	$ 2	$ (1)	$ 11	$ 1
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Commercial Products Revenue [Member] | Futures [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(3)	3	(7)	14
Customer-Related Positions [Member] | Swaps [Member] | Commercial Products Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	26	16	61	33
Customer-Related Positions [Member] | Credit Contracts [Member] | Commercial Products Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	(4)	1	(12)	3
Customer-Related Positions [Member] | Foreign Exchange Rate Contracts [Member] | Commercial Products Revenue [Member] | Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	1		1
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	20	20	59	65
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	20	23	(20)	96
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	154	46	347	144
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Swaps [Member] | Mortgage Banking Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings	215	(68)	513	(224)
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	$ (3)	$ (9)	(18)	18
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			$ (2)	(1)
Asset and Liability Management Positions [Member] | Other Economic Hedges [Member] | Other Derivatives [Member] | Other Noninterest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings				$ 1