GOODWILL AND INTANGIBLE ASSETS - Components of Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	$ 10,108	$ 10,119
Accumulated amortization of Intangible assets (excluding MSRs)	6,670	6,389
Net carrying amount of Intangible assets (excluding MSRs)	3,438	3,730
Gross carrying amount, Mortgage servicing rights (MSRs)	683	691
Mortgage servicing rights (MSRs)	683	691
Gross carrying amount of Intangible assets	10,791	10,810
Accumulated amortization of Intangible assets	6,670	6,389
Total intangible assets	4,121	4,421
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	209	240
Net carrying amount of Intangible assets (excluding MSRs)	209	240
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	5,315	5,302
Accumulated amortization of Intangible assets (excluding MSRs)	4,472	4,365
Net carrying amount of Intangible assets (excluding MSRs)	843	937
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	4,189	4,177
Accumulated amortization of Intangible assets (excluding MSRs)	1,861	1,698
Net carrying amount of Intangible assets (excluding MSRs)	2,328	2,479
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	363	363
Accumulated amortization of Intangible assets (excluding MSRs)	306	290
Net carrying amount of Intangible assets (excluding MSRs)	57	73
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	32	37
Accumulated amortization of Intangible assets (excluding MSRs)	31	36
Net carrying amount of Intangible assets (excluding MSRs)	$ 1	$ 1