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
Mar. 31, 2016	Mar. 31, 2015
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	$ 62	$ 34
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	(47)	41
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	93	59
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	242	115
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	9
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	25	20
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	(2)
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	2
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	1,005	358
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	(1,004)	(350)
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	4
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	$ 17	$ 20

Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Fair Value Hedges [Member]

Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Other Economic Hedges [Member] | Futures and Forwards [Member]

Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Other Economic Hedges [Member] | Options [Member]

Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Other Economic Hedges [Member] | Receive Fixed/Pay Floating Swaps [Member]

Asset and Liability Management Positions [Member] | Interest Rate Contracts [Member] | Mortgage Banking Revenue [Member] | Other Economic Hedges [Member] | Pay Fixed/Receive Floating Swaps [Member]

Asset and Liability Management Positions [Member] | Foreign Exchange Forward Contracts [Member] | Commercial Products Revenue [Member] | Other Economic Hedges [Member]

Asset and Liability Management Positions [Member] | Equity Contracts [Member] | Compensation Expense [Member] | Other Economic Hedges [Member]

Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Options [Member]

Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Receive Fixed/Pay Floating Swaps [Member]

Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Pay Fixed/Receive Floating Swaps [Member]

Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Other Noninterest Income [Member] | Futures [Member]

Customer-Related Positions [Member] | Foreign Exchange Rate Contracts [Member] | Commercial Products Revenue [Member] | Options [Member]

Customer-Related Positions [Member] | Foreign Exchange Rate Contracts [Member] | Commercial Products Revenue [Member] | Forwards, Spots and Swaps [Member]