ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Additional Impaired Loan Information (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	$ 9	$ 8
Average Recorded Investment	1,234	1,028
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1
Average Recorded Investment	441	267
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1
Average Recorded Investment	396	201
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0
Average Recorded Investment	45	66
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	8	7
Average Recorded Investment	793	761
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1
Average Recorded Investment	176	142
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2	2
Average Recorded Investment	146	134
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2	1
Average Recorded Investment	198	187
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	1	1
Average Recorded Investment	57	71
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0
Average Recorded Investment	9	10
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0
Average Recorded Investment	19	13
Education
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	2	2
Average Recorded Investment	152	163
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0
Average Recorded Investment	25	27
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest Income Recognized	0	0
Average Recorded Investment	$ 11	$ 14

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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=66008989&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=66008989&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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