Activity in the ALLL by segment (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	$ 440	$ 156	$ 338
Allowance for Loan and Lease Losses, Write-offs	(591)	(470)	(607)
Loan recoveries	108	129	162
Loans and Leases Receivable, Allowance	1,709	1,752	1,937
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	329	133
Allowance for Loan and Lease Losses, Write-offs	(287)	(117)
Loan recoveries	35	45
Loans and Leases Receivable, Allowance	1,124	1,047	986
Residential Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	(59)	(67)
Allowance for Loan and Lease Losses, Write-offs	(136)	(218)
Loan recoveries	30	42
Loans and Leases Receivable, Allowance	369	534	777
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses	170	90
Allowance for Loan and Lease Losses, Write-offs	(168)	(135)
Loan recoveries	43	42
Loans and Leases Receivable, Allowance	$ 216	$ 171	$ 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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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
-Paragraph 11B
-Subparagraph (g)
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-Publisher FASB
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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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-Name Accounting Standards Codification
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-SubTopic 225
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