GOODWILL AND INTANGIBLE ASSETS - Changes in Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Finite and Indefinite-lived Intangible Assets
Beginning balance	$ 3,763
Acquisitions/renewals/ divestitures	321
Amortization	(280)
Impairments	0
FX translation and other	7
Ending balance	3,811
Mortgage servicing rights (MSRs)	729	$ 665
Total intangible assets	4,540	$ 4,428
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Beginning balance	192
Acquisitions/renewals/ divestitures	20
Amortization	0
Impairments	0
FX translation and other	22
Ending balance	234
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Beginning balance	1,087
Acquisitions/renewals/ divestitures	0
Amortization	(113)
Impairments	0
FX translation and other	0
Ending balance	974
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Beginning balance	2,385
Acquisitions/renewals/ divestitures	290
Amortization	(141)
Impairments	0
FX translation and other	(8)
Ending balance	2,526
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Beginning balance	90
Acquisitions/renewals/ divestitures	11
Amortization	(18)
Impairments	0
FX translation and other	(7)
Ending balance	76
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Beginning balance	1
Acquisitions/renewals/ divestitures	0
Amortization	0
Impairments	0
FX translation and other	0
Ending balance	1
Other
Finite and Indefinite-lived Intangible Assets
Beginning balance	8
Acquisitions/renewals/ divestitures	0
Amortization	(8)
Impairments	0
FX translation and other	0
Ending balance	$ 0