ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Summary of Changes in Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	$ 1,216
Provision charged to income	91	$ 58
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	1,224
Allowance for loan and lease losses
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	1,216	1,195
Charge-offs	(126)	(115)
Recoveries	43	61
Net charge-offs	(83)	(54)
Sales/Other		(2)
Provision charged to income	91	63
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	1,224	1,202
Allowance for loan and lease losses \| Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	596	544
Charge-offs	(13)	(6)
Recoveries	4	28
Net charge-offs	(9)	22
Sales/Other		0
Provision charged to income	46	12
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	633	578
Allowance for loan and lease losses \| Retail
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	620	651
Charge-offs	(113)	(109)
Recoveries	39	33
Net charge-offs	(74)	(76)
Sales/Other		(2)
Provision charged to income	45	51
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	591	624
Reserve for unfunded lending commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	58	61
Credit for unfunded lending commitments	0	(5)
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	58	56
Reserve for unfunded lending commitments \| Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	58	61
Credit for unfunded lending commitments	0	(5)
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	58	56
Reserve for unfunded lending commitments \| Retail
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	0	0
Credit for unfunded lending commitments	0	0
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	0	0
Allowance for loan and lease losses and reserve for off-balance sheet activities, total
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	1,282	1,258
Allowance for loan and lease losses and reserve for off-balance sheet activities, total \| Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	691	634
Allowance for loan and lease losses and reserve for off-balance sheet activities, total \| Retail
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	$ 591	$ 624

Allowance related to loans transferred to held for sale.

No definition available.

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- Definition

Amount of credit for unfunded lending commitments recorded during the reporting period.

+ References

No definition available.

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- Definition

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

+ 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

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

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- Definition

Amount, after recoveries, of loans and leases that have been written-off.

+ References

No definition available.

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section L
-Subsection 1

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
-Paragraph 28
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-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

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-Name Accounting Standards Codification
-Topic 310
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-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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