ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Additional Impaired Loan Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	$ 9	$ 11	$ 27	$ 35
Average Recorded Investment	1,180	1,320	1,106	1,310
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1	4	3
Average Recorded Investment	380	161	330	178
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1	4	2
Average Recorded Investment	340	126	277	133
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0	0	1
Average Recorded Investment	40	35	53	45
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	8	10	23	32
Average Recorded Investment	800	1,159	776	1,132
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	4	3	12
Average Recorded Investment	169	428	161	423
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2	2	5	7
Average Recorded Investment	153	277	151	263
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2	1	5	3
Average Recorded Investment	192	142	182	140
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1	3	3
Average Recorded Investment	64	79	64	80
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0	0	0
Average Recorded Investment	9	10	9	9
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0	0	0
Average Recorded Investment	17	12	14	11
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1	5	5
Average Recorded Investment	159	165	157	160
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0	1	1
Average Recorded Investment	25	29	25	28
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1	1	1
Average Recorded Investment	$ 12	$ 17	$ 13	$ 18

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- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5258-111524

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

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