Activity in the ALLL by segment (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	$ 141	$ 28	$ 243	$ 84
Allowance for Loan and Lease Losses, Write-offs	(167)	(123)	(278)	(254)
Loan recoveries	30	36	57	67
Loans and Leases Receivable, Allowance	1,774	1,834	1,774	1,834	$ 1,770	$ 1,752	$ 1,893	$ 1,937
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	114	33	212	40
Allowance for Loan and Lease Losses, Write-offs	(99)	(31)	(131)	(59)
Loan recoveries	9	15	19	26
Loans and Leases Receivable, Allowance	1,147	993	1,147	993	1,123	1,047	976	986
Residential Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	(4)	(16)	(37)	9
Allowance for Loan and Lease Losses, Write-offs	(33)	(61)	(73)	(129)
Loan recoveries	9	10	15	19
Loans and Leases Receivable, Allowance	439	676	439	676	467	534	743	777
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	31	11	68	35
Allowance for Loan and Lease Losses, Write-offs	(35)	(31)	(74)	(66)
Loan recoveries	12	11	23	22
Loans and Leases Receivable, Allowance	$ 188	$ 165	$ 188	$ 165	$ 180	$ 171	$ 174	$ 174

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
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Amount of expense related to estimated loss from loan and lease transactions.

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-Name Accounting Standards Codification
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