GOODWILL AND INTANGIBLE ASSETS - Components of Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	$ 11,934	$ 15,384
Accumulated amortization of Intangible assets (excluding MSRs)	7,202	10,270
Net carrying amount of Intangible assets (excluding MSRs)	4,732	5,114
Gross carrying amount, Mortgage servicing rights (MSRs)	553	1,564
Mortgage servicing rights (MSRs)	553	1,564
Gross carrying amount of Intangible assets	12,487	16,948
Accumulated amortization of Intangible assets	7,202	10,270
Total intangible assets	5,285	6,678
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	232	210
Accumulated amortization of Intangible assets (excluding MSRs)	0	0
Net carrying amount of Intangible assets (excluding MSRs)	232	210
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	5,377	8,215
Accumulated amortization of Intangible assets (excluding MSRs)	3,798	6,549
Net carrying amount of Intangible assets (excluding MSRs)	1,579	1,666
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	5,045	5,149
Accumulated amortization of Intangible assets (excluding MSRs)	2,357	2,177
Net carrying amount of Intangible assets (excluding MSRs)	2,688	2,972
Core deposit intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	670	801
Accumulated amortization of Intangible assets (excluding MSRs)	656	771
Net carrying amount of Intangible assets (excluding MSRs)	14	30
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	462	474
Accumulated amortization of Intangible assets (excluding MSRs)	269	272
Net carrying amount of Intangible assets (excluding MSRs)	193	202
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	35	31
Accumulated amortization of Intangible assets (excluding MSRs)	31	27
Net carrying amount of Intangible assets (excluding MSRs)	4	4
Other
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	113	504
Accumulated amortization of Intangible assets (excluding MSRs)	91	474
Net carrying amount of Intangible assets (excluding MSRs)	$ 22	$ 30