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, 2017	Mar. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	$ 1,236
Provision charged to income	96	$ 91
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	1,236	1,216
Charge-offs	(133)	(126)
Recoveries	46	43
Net charge-offs	(87)	(83)
Provision charged to income	75	91
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	1,224	1,224
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	663	596
Charge-offs	(24)	(13)
Recoveries	5	4
Net charge-offs	(19)	(9)
Provision charged to income	9	46
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	653	633
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	573	620
Charge-offs	(109)	(113)
Recoveries	41	39
Net charge-offs	(68)	(74)
Provision charged to income	66	45
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	571	591
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	72	58
Provision for unfunded lending commitments	21	0
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	93	58
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	72	58
Provision for unfunded lending commitments	21	0
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	93	58
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
Provision 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	1,317	1,282
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	746	691
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	$ 571	$ 591

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

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.

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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.

+ 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
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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))
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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
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