ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Default of Modified Debt Agreements (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017 USD ($) contract	Jun. 30, 2016 USD ($) contract	Jun. 30, 2017 USD ($) contract	Jun. 30, 2016 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	272	238	536	502
Balance Defaulted \| $	$ 12	$ 12	$ 26	$ 26
Commercial Banking
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	4	9	6	12
Balance Defaulted \| $	$ 1	$ 3	$ 5	$ 3
Commercial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	4	8	5	11
Balance Defaulted \| $	$ 1	$ 3	$ 1	$ 3
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	0	1	1	1
Balance Defaulted \| $	$ 0	$ 0	$ 4	$ 0
Retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	268	229	530	490
Balance Defaulted \| $	$ 11	$ 9	$ 21	$ 23
Residential mortgages
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	41	35	86	89
Balance Defaulted \| $	$ 4	$ 4	$ 10	$ 12
Home equity loans
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	14	32	23	50
Balance Defaulted \| $	$ 1	$ 2	$ 1	$ 3
Home equity lines of credit
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	65	20	100	45
Balance Defaulted \| $	$ 4	$ 1	$ 7	$ 4
Home equity loans serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	9	11	10	21
Balance Defaulted \| $	$ 0	$ 0	$ 0	$ 1
Home equity lines of credit serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1	6	4	11
Balance Defaulted \| $	$ 0	$ 0	$ 0	$ 0
Automobile
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	27	22	61	37
Balance Defaulted \| $	$ 1	$ 1	$ 1	$ 1
Education
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	9	18	16	31
Balance Defaulted \| $	$ 0	$ 1	$ 0	$ 1
Credit cards
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	102	85	228	206
Balance Defaulted \| $	$ 1	$ 0	$ 2	$ 1
Other retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	0	0	2	0
Balance Defaulted \| $	$ 0	$ 0	$ 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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