GOODWILL AND INTANGIBLE ASSETS - Components of Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	$ 10,228	$ 10,371
Accumulated amortization of Intangible assets (excluding MSRs)	6,084	5,960
Net carrying amount of Intangible assets (excluding MSRs)	4,144	4,411
Gross carrying amount, Mortgage servicing rights (MSRs)	409	336
Mortgage servicing rights (MSRs)	409	336
Gross carrying amount of Intangible assets	10,637	10,707
Accumulated amortization of Intangible assets	6,084	5,960
Total intangible assets	4,553	4,747
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	183	190
Net carrying amount of Intangible assets (excluding MSRs)	183	190
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	5,579	5,648
Accumulated amortization of Intangible assets (excluding MSRs)	4,306	4,229
Net carrying amount of Intangible assets (excluding MSRs)	1,273	1,419
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	3,887	3,929
Accumulated amortization of Intangible assets (excluding MSRs)	1,337	1,276
Net carrying amount of Intangible assets (excluding MSRs)	2,550	2,653
Core deposit intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	39	45
Accumulated amortization of Intangible assets (excluding MSRs)	39	44
Net carrying amount of Intangible assets (excluding MSRs)	0	1
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	433	455
Accumulated amortization of Intangible assets (excluding MSRs)	307	314
Net carrying amount of Intangible assets (excluding MSRs)	126	141
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	31	32
Accumulated amortization of Intangible assets (excluding MSRs)	29	30
Net carrying amount of Intangible assets (excluding MSRs)	2	2
Other
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	76	72
Accumulated amortization of Intangible assets (excluding MSRs)	66	67
Net carrying amount of Intangible assets (excluding MSRs)	$ 10	$ 5
Customer Concentration Risk \| American Airlines, Costco, The Home Depot and AT&T \| Intangible Assets, Excluding Mortgage Servicing Rights \| Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Concentration risk, percentage	97.00%	96.00%

No definition available.

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- Definition

Sum of the carrying amounts of all intangible assets, excluding goodwill and excluding mortgage servicing rights, as of the balance sheet date, net of accumulated amortization and impairment charges.

+ References

No definition available.

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This element represents the accumulated amortization of all intangible assets, excluding goodwill and mortgage servicing rights (MSRs), as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

This element represents the gross carrying amounts of all intangible assets, excluding goodwill and mortgage servicing rights (MSRs), as of the balance sheet date.

+ References

No definition available.

+ Details

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This element represents the sum of the carrying amounts of all intangible assets excluding goodwill but including mortgage servicing rights, as of the balance sheet date that is net of accumulated amortization and impairment charges.

+ References

No definition available.

+ Details

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This element represents the accumulated amortization of all intangible assets excluding goodwill but including mortgage servicing rights (MSRs), as of the balance sheet date.

+ References

No definition available.

+ Details

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This element represents the gross carrying amount of intangible assets excluding goodwill but including mortgage servicing rights (MSRs), as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

The amount of mortgage servicing rights (MSRs) as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

This element represents the gross carrying amount of mortgage servicing rights (MSRs) as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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