GOODWILL AND INTANGIBLE ASSETS - Changes in Intangible Assets (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 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	(158)
Amortization	(334)
Impairments	(5)
FX and other	2
Net carrying amount of Intangible assets (excluding MSRs), ending balance	4,071
Mortgage servicing rights (MSRs)	1,924	$ 1,845
Net carrying amount of Intangible assets, balance at end of period	5,995	$ 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	(18)
Net carrying amount of Intangible assets (excluding MSRs), ending balance	272
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	(134)
Impairments	0
FX and other	8
Net carrying amount of Intangible assets (excluding MSRs), ending balance	1,206
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	(22)
Impairments	0
FX and other	(7)
Net carrying amount of Intangible assets (excluding MSRs), ending balance	103
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	(12)
Impairments	0
FX and other	(6)
Net carrying amount of Intangible assets (excluding MSRs), ending balance	143
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	(65)
Amortization	(7)
Impairments	0
FX and other	0
Net carrying amount of Intangible assets (excluding MSRs), ending balance	7
Other
Finite and Indefinite-lived Intangible Assets [Roll Forward]
Net carrying amount of Intangible assets (excluding MSRs), beginning balance	2,485
Acquisitions/ divestitures	(6)
Amortization	(159)
Impairments	(5)
FX and other	25
Net carrying amount of Intangible assets (excluding MSRs), ending balance	$ 2,340