Activity in the Allowance for Credit Losses (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018		Mar. 31, 2019		Dec. 31, 2018		Mar. 31, 2018		Dec. 31, 2017
Components:
Allowance for credit losses	$ 1,751		$ 1,722		$ 1,751		$ 1,722
Provision for loan losses	123		29		279		67
Provision for Other Credit Losses	4	[1]	3	[2]	1	[1]	(7)	[2]
Allowance for Loan and Lease Losses, Write-offs	(113)		(101)		(238)		(207)
Loan recoveries	28		28		56		55
Allowance for Loan and Lease Losses, Adjustments, Other	0				(31)	[3]
Loans and Leases Receivable, Allowance	1,681		1,650		1,681		1,650		$ 1,643		$ 1,615		$ 1,694		$ 1,735
Unfunded commitments reserve	70	[1]	72	[2]	70	[1]	72	[2]	66	[1]	69	[1]	69	[2]	79	[2]
Commercial Portfolio Segment [Member]
Components:
Allowance for credit losses	1,272		1,140		1,272		1,140
Provision for loan losses	82		17		166		1
Provision for Other Credit Losses	4	[1]	3	[2]	1	[1]	(7)	[2]
Allowance for Loan and Lease Losses, Write-offs	(20)		(21)		(53)		(44)
Loan recoveries	4		4		9		10
Allowance for Loan and Lease Losses, Adjustments, Other	0				0
Loans and Leases Receivable, Allowance	1,202		1,068		1,202		1,068		1,136		1,080		1,068		1,101
Unfunded commitments reserve	70	[1]	72	[2]	70	[1]	72	[2]	66	[1]	69	[1]	69	[2]	79	[2]
Consumer Portfolio Segment [Member]
Components:
Allowance for credit losses	479		582		479		582
Provision for loan losses	41		12		113		66
Allowance for Loan and Lease Losses, Write-offs	(93)		(80)		(185)		(163)
Loan recoveries	24		24		47		45
Allowance for Loan and Lease Losses, Adjustments, Other	0				(31)	[3]
Loans and Leases Receivable, Allowance	$ 479		$ 582		$ 479		$ 582		$ 507		$ 535		$ 626		$ 634

[1] The unfunded commitments reserve is recorded in Other liabilities in the Consolidated Balance Sheets.

[2] The unfunded commitments reserve is recorded in Other liabilities in the Consolidated Balance Sheets

[3] Represents the allowance for restructured loans that were transferred from LHFI to LHFS in the first quarter of 2019 and subsequently sold in the second quarter of 2019.