GOODWILL - Goodwill Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning balance	$ 6,876	$ 6,876
Business acquisition	11
Adjustments	0	0
Ending balance	6,887	6,876
Consumer Banking
Goodwill [Roll Forward]
Beginning balance	2,136	2,136
Business acquisition	0
Adjustments	0	0
Ending balance	2,136	2,136
Commercial Banking
Goodwill [Roll Forward]
Beginning balance	4,740	4,740
Business acquisition	11
Adjustments	0	0
Ending balance	$ 4,751	$ 4,740

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

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- Definition

Amount of increase (decrease), classified as other, of an asset representing the future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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