ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Summary of Changes in Allowance for Credit Losses (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance	$ 1,221
Provision charged to income	319us-gaap_ProvisionForLoanAndLeaseLosses	479us-gaap_ProvisionForLoanAndLeaseLosses	413us-gaap_ProvisionForLoanAndLeaseLosses
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	1,195	1,221
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	1,221	1,255	1,698
Charge-offs	(493)	(703)	(1,110)
Recoveries	170	202	235
Net recoveries (charge-offs)	(323)	(501)	(875)
Sales / Other		(13)	(2)
Provision charged to income	297	480	434
Transfer of unallocated reserve to qualitative reserve		0
Loss emergence period change		0
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	1,195	1,221	1,255
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	498	509	691
Charge-offs	(43)	(108)	(257)
Recoveries	58	87	113
Net recoveries (charge-offs)	15	(21)	(144)
Sales / Other		(6)	(2)
Provision charged to income	31	(19)	(36)
Transfer of unallocated reserve to qualitative reserve		35
Loss emergence period change		0
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	544	498	509
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	723	657	816
Charge-offs	(450)	(595)	(853)
Recoveries	112	115	122
Net recoveries (charge-offs)	(338)	(480)	(731)
Sales / Other		(6)	0
Provision charged to income	266	396	572
Transfer of unallocated reserve to qualitative reserve		60
Loss emergence period change		96
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	651	723	657
Allowance for loan and lease losses \| Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Beginning balance		89	191
Charge-offs		0	0
Recoveries		0	0
Net recoveries (charge-offs)		0	0
Sales / Other		(1)	0
Provision charged to income		103	(102)
Transfer of unallocated reserve to qualitative reserve		(95)
Loss emergence period change		(96)
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance		0	89
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	39	40	61
Provision for unfunded lending commitments	22
Credit for unfunded lending commitments		(1)	(21)
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	61	39	40
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	39	40	61
Provision for unfunded lending commitments	22
Credit for unfunded lending commitments		(1)	(21)
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	61	39	40
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
Provision for unfunded lending commitments	0
Credit for unfunded lending commitments		0	0
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance	0	0	0
Reserve for unfunded lending commitments \| Unallocated
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	1,256	1,260	1,295
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	605	537	549
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	651	723	657
Allowance for loan and lease losses and reserve for off-balance sheet activities. Total \| Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan and lease losses / Reserve for unfunded lending commitments, Ending balance		$ 0	$ 89

Amount transferred of unallocated reserve to qualitative reserve during the reporting period.

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Allowance related to loans transferred to held for sale.

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Amount transferred of unallocated reserve to qualitative reserve during the reporting period.

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Amount of credit for unfunded lending commitments recorded during the reporting 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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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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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.

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-SubTopic 210

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-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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-Topic 230

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Amount of expense related to credit loss from transactions other than loan and lease transactions.

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