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, 2019	Mar. 31, 2018
Interest Rate Contract | Customer Contracts | Corporate banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ 6	$ 7
Interest Rate Contract | Customer Contracts | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(7)	0
Interest Rate Contract | Interest Rate Lock Commitments | Mortgage banking net revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	24	13
Commodity Contract | Customer Contracts | Corporate banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	1	2
Commodity Contract | Fair Value Adjustments on Hedges and Derivative Contracts | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	0	0
Foreign Exchange Contract | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	(2)	2
Foreign Exchange Contract | Customer Contracts | Corporate banking revenue
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	12	14
Foreign Exchange Contract | Customer Contracts | Other noninterest income
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	4	(2)
Foreign Exchange Contract | Fair Value Adjustments on Hedges and Derivative Contracts | Other noninterest expense
Derivative Instruments, Gain (Loss)
Net gains (losses) recorded in earnings	$ 0	$ 1