ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Default of Modified Debt Agreements (Details) $ in Millions	3 Months Ended
Mar. 31, 2017 USD ($) contract	Mar. 31, 2016 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	264	295
Balance Defaulted \| $	$ 14	$ 16
Commercial Banking
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	2	3
Balance Defaulted \| $	$ 4	$ 0
Commercial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1	3
Balance Defaulted \| $	$ 0	$ 0
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1	0
Balance Defaulted \| $	$ 4	$ 0
Retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	262	292
Balance Defaulted \| $	$ 10	$ 16
Residential mortgages
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	45	54
Balance Defaulted \| $	$ 6	$ 8
Home equity loans
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	9	49
Balance Defaulted \| $	$ 0	$ 3
Home equity lines of credit
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	35	25
Balance Defaulted \| $	$ 3	$ 3
Home equity loans serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1	10
Balance Defaulted \| $	$ 0	$ 1
Home equity lines of credit serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	3	5
Balance Defaulted \| $	$ 0	$ 0
Automobile
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	34	15
Balance Defaulted \| $	$ 0	$ 0
Education
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	7	13
Balance Defaulted \| $	$ 0	$ 0
Credit cards
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	126	121
Balance Defaulted \| $	$ 1	$ 1
Other retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	2	0
Balance Defaulted \| $	$ 0	$ 0

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524

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Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

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