Activity in the ALLL by segment (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
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	$ 123		$ 29		$ 279		$ 67
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)	[1]
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	[2]	72	[3]	70	[2]	72	[3]	66	[2]	69	[2]	69	[3]	79	[3]
Provision for Other Credit Losses	4	[2]	3	[3]	1	[2]	(7)	[3]
Financing Receivable, Allowance for Credit Losses	1,751		1,722		1,751		1,722
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	82		17		166		1
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	[2]	72	[3]	70	[2]	72	[3]	66	[2]	69	[2]	69	[3]	79	[3]
Provision for Other Credit Losses	4	[2]	3	[3]	1	[2]	(7)	[3]
Financing Receivable, Allowance for Credit Losses	1,272		1,140		1,272		1,140
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
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)	[1]
Loans and Leases Receivable, Allowance	479		582		479		582		$ 507		$ 535		$ 626		$ 634
Financing Receivable, Allowance for Credit Losses	$ 479		$ 582		$ 479		$ 582

[1] 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.

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

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