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, 2018 USD ($) contract	Sep. 30, 2017 USD ($) contract	Sep. 30, 2018 USD ($) contract	Sep. 30, 2017 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	260	279	781	832
Balance Defaulted \| $	$ 42	$ 14	$ 82	$ 40
Commercial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	9	2	16	8
Balance Defaulted \| $	$ 32	$ 4	$ 52	$ 9
Commercial \| Commercial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	9	2	15	7
Balance Defaulted \| $	$ 32	$ 4	$ 52	$ 5
Commercial \| Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	0	0	1	1
Balance Defaulted \| $	$ 0	$ 0	$ 0	$ 4
Retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	251	277	765	824
Balance Defaulted \| $	$ 10	$ 10	$ 30	$ 31
Retail \| Residential mortgages
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	33	35	103	121
Balance Defaulted \| $	$ 4	$ 5	$ 12	$ 15
Retail \| Home equity loans
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	6	12	24	35
Balance Defaulted \| $	$ 0	$ 0	$ 1	$ 1
Retail \| Home equity lines of credit
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	59	55	165	152
Balance Defaulted \| $	$ 5	$ 4	$ 13	$ 11
Retail \| Home equity loans serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	3	6	13	16
Balance Defaulted \| $	$ 0	$ 0	$ 0	$ 0
Retail \| Home equity lines of credit serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	2	4	3	8
Balance Defaulted \| $	$ 0	$ 0	$ 0	$ 0
Retail \| Automobile
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	40	42	116	103
Balance Defaulted \| $	$ 0	$ 0	$ 1	$ 1
Retail \| Education
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1	5	13	41
Balance Defaulted \| $	$ 0	$ 1	$ 1	$ 1
Retail \| Credit cards
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	106	116	327	344
Balance Defaulted \| $	$ 1	$ 0	$ 2	$ 2
Retail \| Other retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1	2	1	4
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://fasb.org/us-gaap/role/ref/legacyRef
-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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