ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Nonaccrual Loans and Leases by Class (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	$ 1,277	$ 703
90 days past due and accruing	28
Nonaccrual with no related ACL	353
Commercial
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	760	245
90 days past due and accruing	3
Nonaccrual with no related ACL	36
Commercial \| Commercial
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	435	240
90 days past due and accruing	3
Nonaccrual with no related ACL	33
Commercial \| Commercial real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	323	2
90 days past due and accruing	0
Nonaccrual with no related ACL	3
Commercial \| Leases
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	2	3
90 days past due and accruing	0
Nonaccrual with no related ACL	0
Retail
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	517	458
90 days past due and accruing	25
Nonaccrual with no related ACL	317
Retail \| Residential mortgages
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	131	93
90 days past due and accruing	17
Nonaccrual with no related ACL	101
Retail \| Home equity
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	265	246
90 days past due and accruing	0
Nonaccrual with no related ACL	192
Retail \| Automobile
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	80	67
90 days past due and accruing	0
Nonaccrual with no related ACL	18
Retail \| Education
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	16	18
90 days past due and accruing	2
Nonaccrual with no related ACL	5
Retail \| Other retail
Financing Receivable, Past Due [Line Items]
Nonaccrual loans and leases	25	$ 34
90 days past due and accruing	6
Nonaccrual with no related ACL	$ 1

Amount of financing receivable on nonaccrual status with no allowance for credit loss.

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- Definition

Amount of financing receivable 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
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- Definition

Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 50
-Paragraph 16
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-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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