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	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 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			267	$ 211
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	$ 1,240		1,240
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	1,246	$ 1,201	1,216	1,195
Charge-offs	(145)	(120)	(384)	(356)
Recoveries	62	45	153	149
Net (charge-offs) recoveries	(83)	(75)	(231)	(207)
Sales/Other		2		0
Provision charged to income	77	73	255	213
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	1,240	1,201	1,240	1,201
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	676	565	596	544
Charge-offs	(33)	(11)	(53)	(32)
Recoveries	14	6	23	42
Net (charge-offs) recoveries	(19)	(5)	(30)	10
Sales/Other		0		0
Provision charged to income	(2)	15	89	21
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	655	575	655	575
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	570	636	620	651
Charge-offs	(112)	(109)	(331)	(324)
Recoveries	48	39	130	107
Net (charge-offs) recoveries	(64)	(70)	(201)	(217)
Sales/Other		2		0
Provision charged to income	79	58	166	192
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	585	626	585	626
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	61	56	58	61
Credit for unfunded lending commitments	9	3	12	(2)
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	70	59	70	59
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	61	56	58	61
Credit for unfunded lending commitments	9	3	12	(2)
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	70	59	70	59
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	0	0
Credit for unfunded lending commitments	0	0	0	0
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	0	0	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	1,310	1,260	1,310	1,260
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	725	634	725	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	$ 585	$ 626	$ 585	$ 626

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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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

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

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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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
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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
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-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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Amount of expense related to estimated loss from loan and lease transactions.

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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

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