ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Default of Modified Debt Agreements (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017 USD ($) contract	Sep. 30, 2016 USD ($) contract	Sep. 30, 2017 USD ($) contract	Sep. 30, 2016 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	279	311	832	788
Balance Defaulted \| $	$ 14	$ 13	$ 40	$ 39
Commercial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	2	5	8	17
Balance Defaulted \| $	$ 4	$ 1	$ 9	$ 4
Commercial \| Commercial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	2	5	7	16
Balance Defaulted \| $	$ 4	$ 1	$ 5	$ 4
Commercial \| Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	0	0	1	1
Balance Defaulted \| $	$ 0	$ 0	$ 4	$ 0
Retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	277	306	824	771
Balance Defaulted \| $	$ 10	$ 12	$ 31	$ 35
Retail \| Residential mortgages
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	35	57	121	146
Balance Defaulted \| $	$ 5	$ 7	$ 15	$ 19
Retail \| Home equity loans
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	12	14	35	39
Balance Defaulted \| $	$ 0	$ 0	$ 1	$ 3
Retail \| Home equity lines of credit
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	55	48	152	93
Balance Defaulted \| $	$ 4	$ 4	$ 11	$ 8
Retail \| Home equity loans serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	6	7	16	28
Balance Defaulted \| $	$ 0	$ 0	$ 0	$ 1
Retail \| Home equity lines of credit serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	4	3	8	14
Balance Defaulted \| $	$ 0	$ 0	$ 0	$ 0
Retail \| Automobile
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	42	43	103	80
Balance Defaulted \| $	$ 0	$ 0	$ 1	$ 1
Retail \| Education
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	5	15	41	46
Balance Defaulted \| $	$ 1	$ 0	$ 1	$ 1
Retail \| Credit cards
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	116	117	344	323
Balance Defaulted \| $	$ 0	$ 1	$ 2	$ 2
Retail \| Other retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	2	2	4	2
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=84173941&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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