GOODWILL AND INTANGIBLE ASSETS - Changes in Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Finite and Indefinite-lived Intangible Assets [Roll Forward]
Net carrying amount of Intangible assets (excluding MSRs), beginning balance	$ 4,566
Acquisitions/ divestitures	(176)
Amortization	(479)
Impairments	(5)
FX and other	(26)
Net carrying amount of Intangible assets (excluding MSRs), ending balance	3,880
Mortgage servicing rights (MSRs)	1,766	$ 1,845
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 [Roll Forward]
Net carrying amount of Intangible assets (excluding MSRs), beginning balance	290
Acquisitions/ divestitures	0
Amortization	0
Impairments	0
FX and other	(34)
Net carrying amount of Intangible assets (excluding MSRs), ending balance	256
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets [Roll Forward]
Net carrying amount of Intangible assets (excluding MSRs), beginning balance	1,332
Acquisitions/ divestitures	0
Amortization	(199)
Impairments	0
FX and other	5
Net carrying amount of Intangible assets (excluding MSRs), ending balance	1,138
Core deposit intangibles
Finite and Indefinite-lived Intangible Assets [Roll Forward]
Net carrying amount of Intangible assets (excluding MSRs), beginning balance	132
Acquisitions/ divestitures	0
Amortization	(32)
Impairments	0
FX and other	(9)
Net carrying amount of Intangible assets (excluding MSRs), ending balance	91
Other customer relationships
Finite and Indefinite-lived Intangible Assets [Roll Forward]
Net carrying amount of Intangible assets (excluding MSRs), beginning balance	248
Acquisitions/ divestitures	(87)
Amortization	(18)
Impairments	0
FX and other	(3)
Net carrying amount of Intangible assets (excluding MSRs), ending balance	140
Present value of future profits
Finite and Indefinite-lived Intangible Assets [Roll Forward]
Net carrying amount of Intangible assets (excluding MSRs), beginning balance	79
Acquisitions/ divestitures	(68)
Amortization	(4)
Impairments	0
FX and other	(1)
Net carrying amount of Intangible assets (excluding MSRs), ending balance	6
Other
Finite and Indefinite-lived Intangible Assets [Roll Forward]
Net carrying amount of Intangible assets (excluding MSRs), beginning balance	2,485
Acquisitions/ divestitures	(21)
Amortization	(226)
Impairments	(5)
FX and other	16
Net carrying amount of Intangible assets (excluding MSRs), ending balance	$ 2,249