GOODWILL AND INTANGIBLE ASSETS - Components of Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	$ 10,371	$ 12,271
Accumulated amortization of Intangible assets (excluding MSRs)	5,960	7,944
Net carrying amount of intangible assets (excluding MSRs)	4,411	4,327
Gross carrying amount, Mortgage servicing rights (MSRs)	336	495
Mortgage servicing rights (MSRs)	336	495
Gross carrying amount of Intangible assets	10,707	12,766
Accumulated amortization of intangible assets	5,960	7,944
Total intangible assets	4,747	4,822
Intangible assets amortization expense	419	564	$ 557
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2021	364
2022	350
2023	351
2024	365
2025	370
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	190	228
Accumulated amortization of Intangible assets (excluding MSRs)	0	0
Net carrying amount of intangible assets (excluding MSRs)	190	228
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	5,648	5,676
Accumulated amortization of Intangible assets (excluding MSRs)	4,229	4,059
Net carrying amount of intangible assets (excluding MSRs)	1,419	1,617
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	3,929	5,393
Accumulated amortization of Intangible assets (excluding MSRs)	1,276	3,069
Net carrying amount of intangible assets (excluding MSRs)	2,653	2,324
Core deposit intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	45	434
Accumulated amortization of Intangible assets (excluding MSRs)	44	433
Net carrying amount of intangible assets (excluding MSRs)	1	1
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	455	424
Accumulated amortization of Intangible assets (excluding MSRs)	314	275
Net carrying amount of intangible assets (excluding MSRs)	141	149
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	32	34
Accumulated amortization of Intangible assets (excluding MSRs)	30	31
Net carrying amount of intangible assets (excluding MSRs)	2	3
Other
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	72	82
Accumulated amortization of Intangible assets (excluding MSRs)	67	77
Net carrying amount of intangible assets (excluding MSRs)	$ 5	$ 5
American Airlines, Sears, The Home Depot and Costco \| Intangible Assets, Excluding Mortgage Servicing Rights \| Customer Concentration Risk \| Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Intangible assets, percent	96.00%	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.

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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.

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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.

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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.

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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.

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

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No definition available.

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

+ References

No definition available.

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- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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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

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- Definition

Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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