LOANS - Corporate Troubled Debt Restructurings (Details) - Corporate - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Financing receivable impaired
Carrying Value	$ 173	$ 560
Period within which default occurred post-modification	1 year
Number of days past due, default status	60 days
Carrying Value	$ 564	818
TDR in payment default	$ 70	72
Commercial banking
Financing receivable impaired
Number of days past due, default status	90 days
Commercial and industrial
Financing receivable impaired
Carrying Value	$ 113	509
Carrying Value	414	617
TDR in payment default	70	72
Financial institutions
Financing receivable impaired
Carrying Value		15
Carrying Value	25	48
TDR in payment default	0	0
Mortgage and real estate
Financing receivable impaired
Carrying Value	60	36
Carrying Value	123	101
TDR in payment default	0	0
Lease financing
Financing receivable impaired
Carrying Value	0	7
TDR in payment default	0	0
Other
Financing receivable impaired
Carrying Value	2	45
TDR in payment default	0	0
TDRs involving changes in the amount and/or timing of principal payments
Financing receivable impaired
Carrying Value	8	131
TDRs involving changes in the amount and/or timing of principal payments \| Commercial and industrial
Financing receivable impaired
Carrying Value	5	131
TDRs involving changes in the amount and/or timing of principal payments \| Financial institutions
Financing receivable impaired
Carrying Value		0
TDRs involving changes in the amount and/or timing of principal payments \| Mortgage and real estate
Financing receivable impaired
Carrying Value	3	0
TDRs involving vhanges in the amount and/or timing of interest payments
Financing receivable impaired
Carrying Value	8	7
TDRs involving vhanges in the amount and/or timing of interest payments \| Commercial and industrial
Financing receivable impaired
Carrying Value	8	7
TDRs involving vhanges in the amount and/or timing of interest payments \| Financial institutions
Financing receivable impaired
Carrying Value		0
TDRs involving vhanges in the amount and/or timing of interest payments \| Mortgage and real estate
Financing receivable impaired
Carrying Value	0	0
TDRs invovling changes in the amount and/or timing of both principal and interest payments
Financing receivable impaired
Carrying Value	157	422
TDRs invovling changes in the amount and/or timing of both principal and interest payments \| Commercial and industrial
Financing receivable impaired
Carrying Value	100	371
TDRs invovling changes in the amount and/or timing of both principal and interest payments \| Financial institutions
Financing receivable impaired
Carrying Value		15
TDRs invovling changes in the amount and/or timing of both principal and interest payments \| Mortgage and real estate
Financing receivable impaired
Carrying Value	$ 57	$ 36

This represents the period within which the payment default occurred after the loan modification.

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- Definition

Represents the classified default number of days for which the loan is past due.

+ References

No definition available.

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- Definition

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+ References

No definition available.

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- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

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- Definition

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

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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