Allowance for Credit Losses - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan delinquent period	90 days
Minimum delinquency period for loan level collectability analysis consumer mortgage	150 days
Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loans for which partial charge-off has been recognized	$ 55	$ 63
Mortgage loans, customer balance outstanding	20	27
Home Equity Loans and Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loans for which partial charge-off has been recognized	21	18
Mortgage loans, customer balance outstanding	$ 28	$ 28

The threshold number of days in delinquency at which criticized loans are generally classified as non-accrual.

No definition available.

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- Definition

Loans and leases receivable net of partial charge off.

+ References

No definition available.

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- Definition

Minimum delinquency period threshold at which residential real estate loans and outstanding balances of home equity lines of credit are generally evaluated for collectability on a loan-by-loan basis giving consideration to estimated collateral values.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The carrying amount of the outstanding balance due under the mortgage loan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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