GOODWILL AND INTANGIBLE ASSETS - Components of Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	$ 12,323	$ 12,181
Accumulated amortization of Intangible assets (excluding MSRs)	7,678	7,545
Net carrying amount of Intangible assets (excluding MSRs)	4,645	4,636
Gross carrying amount, Mortgage servicing rights (MSRs)	551	584
Mortgage servicing rights (MSRs)	551	584
Gross carrying amount of Intangible assets	12,874	12,765
Accumulated amortization of Intangible assets	7,678	7,545
Total intangible assets	5,196	5,220
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	220	218
Accumulated amortization of Intangible assets (excluding MSRs)	0	0
Net carrying amount of Intangible assets (excluding MSRs)	220	218
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	5,734	5,733
Accumulated amortization of Intangible assets (excluding MSRs)	3,985	3,936
Net carrying amount of Intangible assets (excluding MSRs)	1,749	1,797
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	5,375	5,225
Accumulated amortization of Intangible assets (excluding MSRs)	2,875	2,791
Net carrying amount of Intangible assets (excluding MSRs)	2,500	2,434
Core deposit intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	424	419
Accumulated amortization of Intangible assets (excluding MSRs)	422	415
Net carrying amount of Intangible assets (excluding MSRs)	2	4
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	453	470
Accumulated amortization of Intangible assets (excluding MSRs)	288	299
Net carrying amount of Intangible assets (excluding MSRs)	165	171
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	33	32
Accumulated amortization of Intangible assets (excluding MSRs)	29	29
Net carrying amount of Intangible assets (excluding MSRs)	4	3
Other
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	84	84
Accumulated amortization of Intangible assets (excluding MSRs)	79	75
Net carrying amount of Intangible assets (excluding MSRs)	$ 5	$ 9
Customer Concentration Risk \| American Airlines, Sears, The Home Depot, Costco 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%	97.00%

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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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.

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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.

+ Details

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- Definition

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

+ References

No definition available.

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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://fasb.org/us-gaap/role/ref/legacyRef
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