FAIR VALUE MEASUREMENTS - Schedule of Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets
Securities available for sale	$ 19,041us-gaap_AvailableForSaleSecurities	$ 18,656us-gaap_AvailableForSaleSecurities
Loans held for sale	322	256
Derivative assets	742us-gaap_DerivativeAssets	629us-gaap_DerivativeAssets
Liabilities
Derivative liabilities	616us-gaap_DerivativeLiabilities	612us-gaap_DerivativeLiabilities
Fair Value Measurement [Domain]
Assets
Securities available for sale	19,041	18,656
Loans held for sale	322	256
Derivative assets	1,006	790
Venture capital investments and other investments	6	5
Total assets	20,375	19,707
Liabilities
Derivative liabilities	880	773
Total liabilities	880	773
Fair Value Measurement [Domain] \| Interest rate swaps
Assets
Derivative assets	744	613
Liabilities
Derivative liabilities	624	600
Fair Value Measurement [Domain] \| Foreign exchange contracts
Assets
Derivative assets	253	170
Liabilities
Derivative liabilities	247	164
Fair Value Measurement [Domain] \| Other contracts
Assets
Derivative assets	9	7
Liabilities
Derivative liabilities	9	9
Fair Value Measurement [Domain] \| Mortgage-backed securities
Assets
Securities available for sale	18,996	18,606
Fair Value Measurement [Domain] \| State and political subdivisions
Assets
Securities available for sale	10	10
Fair Value Measurement [Domain] \| Equity securities
Assets
Securities available for sale	20	25
Fair Value Measurement [Domain] \| U.S. Treasury
Assets
Securities available for sale	15	15
Fair Value Measurement [Domain] \| Residential loans held for sale
Assets
Loans held for sale	265	213
Fair Value Measurement [Domain] \| Commercial real estate loans held for sale
Assets
Loans held for sale	57	43
Fair Value Measurement [Domain] \| Level 1
Assets
Securities available for sale	17	23
Loans held for sale	0	0
Derivative assets	0	0
Venture capital investments and other investments	0	0
Total assets	17	23
Liabilities
Derivative liabilities	0	0
Total liabilities	0	0
Fair Value Measurement [Domain] \| Level 1 \| Interest rate swaps
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value Measurement [Domain] \| Level 1 \| Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value Measurement [Domain] \| Level 1 \| Other contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value Measurement [Domain] \| Level 1 \| Mortgage-backed securities
Assets
Securities available for sale	0	0
Fair Value Measurement [Domain] \| Level 1 \| State and political subdivisions
Assets
Securities available for sale	0	0
Fair Value Measurement [Domain] \| Level 1 \| Equity securities
Assets
Securities available for sale	2	8
Fair Value Measurement [Domain] \| Level 1 \| U.S. Treasury
Assets
Securities available for sale	15	15
Fair Value Measurement [Domain] \| Level 1 \| Residential loans held for sale
Assets
Loans held for sale	0	0
Fair Value Measurement [Domain] \| Level 1 \| Commercial real estate loans held for sale
Assets
Loans held for sale	0	0
Fair Value Measurement [Domain] \| Level 2
Assets
Securities available for sale	19,024	18,633
Loans held for sale	322	256
Derivative assets	1,006	790
Venture capital investments and other investments	5	0
Total assets	20,357	19,679
Liabilities
Derivative liabilities	880	773
Total liabilities	880	773
Fair Value Measurement [Domain] \| Level 2 \| Interest rate swaps
Assets
Derivative assets	744	613
Liabilities
Derivative liabilities	624	600
Fair Value Measurement [Domain] \| Level 2 \| Foreign exchange contracts
Assets
Derivative assets	253	170
Liabilities
Derivative liabilities	247	164
Fair Value Measurement [Domain] \| Level 2 \| Other contracts
Assets
Derivative assets	9	7
Liabilities
Derivative liabilities	9	9
Fair Value Measurement [Domain] \| Level 2 \| Mortgage-backed securities
Assets
Securities available for sale	18,996	18,606
Fair Value Measurement [Domain] \| Level 2 \| State and political subdivisions
Assets
Securities available for sale	10	10
Fair Value Measurement [Domain] \| Level 2 \| Equity securities
Assets
Securities available for sale	18	17
Fair Value Measurement [Domain] \| Level 2 \| U.S. Treasury
Assets
Securities available for sale	0	0
Fair Value Measurement [Domain] \| Level 2 \| Residential loans held for sale
Assets
Loans held for sale	265	213
Fair Value Measurement [Domain] \| Level 2 \| Commercial real estate loans held for sale
Assets
Loans held for sale	57	43
Fair Value Measurement [Domain] \| Level 3
Assets
Securities available for sale	0	0
Loans held for sale	0	0
Derivative assets	0	0
Venture capital investments and other investments	1	5
Total assets	1	5
Liabilities
Derivative liabilities	0	0
Total liabilities	0	0
Fair Value Measurement [Domain] \| Level 3 \| Interest rate swaps
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value Measurement [Domain] \| Level 3 \| Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value Measurement [Domain] \| Level 3 \| Other contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value Measurement [Domain] \| Level 3 \| Mortgage-backed securities
Assets
Securities available for sale	0	0
Fair Value Measurement [Domain] \| Level 3 \| State and political subdivisions
Assets
Securities available for sale	0	0
Fair Value Measurement [Domain] \| Level 3 \| Equity securities
Assets
Securities available for sale	0	0
Fair Value Measurement [Domain] \| Level 3 \| U.S. Treasury
Assets
Securities available for sale	0	0
Fair Value Measurement [Domain] \| Level 3 \| Residential loans held for sale
Assets
Loans held for sale	0	0
Fair Value Measurement [Domain] \| Level 3 \| Commercial real estate loans held for sale
Assets
Loans held for sale	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13495-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226008-175313

+ Details

Name:	us-gaap_DerivativeAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

+ Details

Name:	us-gaap_DerivativeLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancialLiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19190-110258

+ Details

Name:	us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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=28367877&loc=d3e4428-111522

+ Details

Name:	us-gaap_LoansReceivableHeldForSaleAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_FairValueDisclosureItemAmountsDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: