GOODWILL AND INTANGIBLE ASSETS - Changes in Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Finite and Indefinite-lived Intangible Assets
Net carrying amount at December 31, 2017, Intangible assets (excluding MSRs)	$ 4,588
Acquisitions/ divestitures	429
Amortization	(413)
FX translation and other	(6)
Net carrying amount at September 30, 2018, Intangible assets (excluding MSRs)	4,598	$ 4,588
Mortgage servicing rights (MSRs)	618	558
Total intangible assets	5,216	5,146
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Net carrying amount at December 31, 2017, Intangible assets (excluding MSRs)	244
Acquisitions/ divestitures	0
Amortization	0
FX translation and other	(17)
Net carrying amount at September 30, 2018, Intangible assets (excluding MSRs)	227	244
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Net carrying amount at December 31, 2017, Intangible assets (excluding MSRs)	1,539
Acquisitions/ divestitures	429
Amortization	(124)
FX translation and other	(2)
Net carrying amount at September 30, 2018, Intangible assets (excluding MSRs)	1,842	1,539
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Net carrying amount at December 31, 2017, Intangible assets (excluding MSRs)	2,589
Acquisitions/ divestitures	0
Amortization	(255)
FX translation and other	0
Net carrying amount at September 30, 2018, Intangible assets (excluding MSRs)	2,334	2,589
Core deposit intangibles
Finite and Indefinite-lived Intangible Assets
Net carrying amount at December 31, 2017, Intangible assets (excluding MSRs)	11
Acquisitions/ divestitures	0
Amortization	(6)
FX translation and other	0
Net carrying amount at September 30, 2018, Intangible assets (excluding MSRs)	5	11
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Net carrying amount at December 31, 2017, Intangible assets (excluding MSRs)	187
Acquisitions/ divestitures	0
Amortization	(19)
FX translation and other	6
Net carrying amount at September 30, 2018, Intangible assets (excluding MSRs)	174	187
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Net carrying amount at December 31, 2017, Intangible assets (excluding MSRs)	4
Acquisitions/ divestitures	0
Amortization	0
FX translation and other	0
Net carrying amount at September 30, 2018, Intangible assets (excluding MSRs)	4	4
Other
Finite and Indefinite-lived Intangible Assets
Net carrying amount at December 31, 2017, Intangible assets (excluding MSRs)	14
Acquisitions/ divestitures	0
Amortization	(9)
FX translation and other	7
Net carrying amount at September 30, 2018, Intangible assets (excluding MSRs)	$ 12	$ 14
American Airlines, Sears, The Home Depot, Costco and AT&T \| Customer Concentration Risk \| Intangible Assets, Excluding Mortgage Servicing Rights \| Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Concentration risk, percentage	97.00%	97.00%

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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.

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Intangible Assets, Excluding Mortgage Servicing Rights Acquisitions (Divestitures)

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This element represents the aggregate amount of amortization of intangible assets excluding mortgage servicing rights (MSRs) during the period.

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This element represents net changes to the recorded value of intangible assets excluding mortgage servicing rights (MSRs), due to foreign currency translation adjustments and purchase accounting adjustments.

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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.

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

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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.

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