Derivatives (Net Gains (Losses) Recorded in the Consolidated Statements of Income Relating to Free-Standing Derivative Instruments Used For Customer Accommodation) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ 350	$ 60
Interest Rate Contract | Customer Contracts | Commercial Banking Revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	14	6
Interest Rate Contract | Fair Value Adjustments on Hedges and Derivative Contracts | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(33)	(7)
Interest Rate Contract | Interest Rate Lock Commitments | Mortgage Banking Revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	100	24
Commodity Contract | Customer Contracts | Commercial Banking Revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	3	1
Commodity Contract | Fair Value Adjustments on Hedges and Derivative Contracts | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(1)	0
Foreign Exchange Contract | Customer Contracts | Commercial Banking Revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	13	12
Foreign Exchange Contract | Customer Contracts | Other Noninterest Income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	6	4
Foreign Exchange Contract | Fair Value Adjustments on Hedges and Derivative Contracts | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ (2)	$ 0