GOODWILL AND INTANGIBLE ASSETS - Components of Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Finite and Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount of Intangible assets (excluding MSRs)	$ 14,643	$ 15,098
Accumulated amortization of Intangible assets (excluding MSRs)	10,763	10,532
Net carrying amount of Intangible assets (excluding MSRs)	3,880	4,566
Gross carrying amount, Mortgage servicing rights (MSRs)	1,766	1,845
Mortgage servicing rights (MSRs)	1,766	1,845
Gross carrying amount of Intangible assets	16,409	16,943
Accumulated amortization of Intangible assets	10,763	10,532
Net carrying amount of Intangible assets, balance at end of period	5,646	6,411
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount of Intangible assets (excluding MSRs)	256	290
Accumulated amortization of Intangible assets (excluding MSRs)	0	0
Net carrying amount of Intangible assets (excluding MSRs)	256	290
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount of Intangible assets (excluding MSRs)	7,595	7,626
Accumulated amortization of Intangible assets (excluding MSRs)	6,457	6,294
Net carrying amount of Intangible assets (excluding MSRs)	1,138	1,332
Core deposit intangibles
Finite and Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount of Intangible assets (excluding MSRs)	1,058	1,153
Accumulated amortization of Intangible assets (excluding MSRs)	967	1,021
Net carrying amount of Intangible assets (excluding MSRs)	91	132
Other customer relationships
Finite and Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount of Intangible assets (excluding MSRs)	478	579
Accumulated amortization of Intangible assets (excluding MSRs)	338	331
Net carrying amount of Intangible assets (excluding MSRs)	140	248
Present value of future profits
Finite and Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount of Intangible assets (excluding MSRs)	159	233
Accumulated amortization of Intangible assets (excluding MSRs)	153	154
Net carrying amount of Intangible assets (excluding MSRs)	6	79
Other
Finite and Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount of Intangible assets (excluding MSRs)	5,097	5,217
Accumulated amortization of Intangible assets (excluding MSRs)	2,848	2,732
Net carrying amount of Intangible assets (excluding MSRs)	$ 2,249	$ 2,485