ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Default of Modified Debt Agreements (Details) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($) contract	Dec. 31, 2015 USD ($) contract	Dec. 31, 2014 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1,074	1,288	2,037
Balance Defaulted \| $	$ 60	$ 52	$ 97
Commercial Banking
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	23	23	40
Balance Defaulted \| $	$ 13	$ 2	$ 13
Commercial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	22	23	37
Balance Defaulted \| $	$ 13	$ 2	$ 12
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1	0	3
Balance Defaulted \| $	$ 0	$ 0	$ 1
Retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	1,051	1,265	1,997
Balance Defaulted \| $	$ 47	$ 50	$ 84
Residential mortgages
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	187	168	301
Balance Defaulted \| $	$ 24	$ 21	$ 35
Home equity loans
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	50	184	329
Balance Defaulted \| $	$ 3	$ 13	$ 24
Home equity lines of credit
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	155	131	229
Balance Defaulted \| $	$ 13	$ 7	$ 12
Home equity loans serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	37	43	60
Balance Defaulted \| $	$ 1	$ 1	$ 2
Home equity lines of credit serviced by others
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	17	22	20
Balance Defaulted \| $	$ 0	$ 1	$ 0
Automobile
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	110	87	112
Balance Defaulted \| $	$ 2	$ 1	$ 1
Student
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	59	171	355
Balance Defaulted \| $	$ 1	$ 3	$ 7
Credit cards
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	433	455	579
Balance Defaulted \| $	$ 3	$ 3	$ 3
Other retail
Financing Receivable, Modifications [Line Items]
Number of Contracts \| contract	3	4	12
Balance Defaulted \| $	$ 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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