LOANS AND LEASES - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	$ 478	$ 497
Other loans held for sale	322	221
Level 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	478	497
Other loans held for sale	0	0
Level 2 \| Residential loans held for sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	289	326
Level 2 \| Commercial real estate loans held for sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale	189	171
Retail \| Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral for FHLB borrowed funds	25,400	24,900
Loans pledged as collateral to support the contingent ability to borrow at the FRB discount window	$ 17,800	$ 18,100

The amount of other loans receivable that will be sold to other entities.

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- Definition

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+ References

No definition available.

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- Definition

The face amount of loans that will be sold to other entities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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- Definition

The carrying amount, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of FHLB debt obligations, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

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- Definition

The carrying amount, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of other debt obligations, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

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