LOANS - Corporate Troubled Debt Restructurings (Details) - Corporate - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Financing receivable impaired
Carrying value of TDRs modified during the period	$ 305	$ 219
Period within which default occurred post-modification	1 year
Number of days past due, default status	60 days
TDR balances	$ 726	718
TDR in payment default	$ 35	111
Commercial banking
Financing receivable impaired
Number of days past due, default status	90 days
Commercial and industrial
Financing receivable impaired
Carrying value of TDRs modified during the period	$ 283	159
TDR balances	603	568
TDR in payment default	35	111
Financial institutions
Financing receivable impaired
TDR balances	0	25
TDR in payment default	0	0
Mortgage and real estate
Financing receivable impaired
Carrying value of TDRs modified during the period	16	60
TDR balances	79	123
TDR in payment default	0	0
Lease financing
Financing receivable impaired
TDR balances	0	0
TDR in payment default	0	0
Other
Financing receivable impaired
Carrying value of TDRs modified during the period	6
TDR balances	44	2
TDR in payment default	0	0
TDRs involving changes in the amount and/or timing of principal payments
Financing receivable impaired
Carrying value of TDRs modified during the period	25	8
TDRs involving changes in the amount and/or timing of principal payments \| Commercial and industrial
Financing receivable impaired
Carrying value of TDRs modified during the period	19	5
TDRs involving changes in the amount and/or timing of principal payments \| Mortgage and real estate
Financing receivable impaired
Carrying value of TDRs modified during the period	0	3
TDRs involving changes in the amount and/or timing of principal payments \| Other
Financing receivable impaired
Carrying value of TDRs modified during the period	6
TDRs involving vhanges in the amount and/or timing of interest payments
Financing receivable impaired
Carrying value of TDRs modified during the period	0	8
TDRs involving vhanges in the amount and/or timing of interest payments \| Commercial and industrial
Financing receivable impaired
Carrying value of TDRs modified during the period	0	8
TDRs involving vhanges in the amount and/or timing of interest payments \| Mortgage and real estate
Financing receivable impaired
Carrying value of TDRs modified during the period	0	0
TDRs involving vhanges in the amount and/or timing of interest payments \| Other
Financing receivable impaired
Carrying value of TDRs modified during the period	0
TDRs invovling changes in the amount and/or timing of both principal and interest payments
Financing receivable impaired
Carrying value of TDRs modified during the period	280	203
TDRs invovling changes in the amount and/or timing of both principal and interest payments \| Commercial and industrial
Financing receivable impaired
Carrying value of TDRs modified during the period	264	146
TDRs invovling changes in the amount and/or timing of both principal and interest payments \| Mortgage and real estate
Financing receivable impaired
Carrying value of TDRs modified during the period	16	$ 57
TDRs invovling changes in the amount and/or timing of both principal and interest payments \| Other
Financing receivable impaired
Carrying value of TDRs modified during the period	$ 0

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

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+ References

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- Definition

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- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

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-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18845-111554

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Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

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