GOODWILL AND INTANGIBLE ASSETS - Components of Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	$ 15,817	$ 14,107
Accumulated amortization of Intangible assets (excluding MSRs)	10,459	10,386
Net carrying amount of Intangible assets (excluding MSRs)	5,358	3,721
Gross carrying amount, Mortgage servicing rights (MSRs)	1,270	1,781
Mortgage servicing rights (MSRs)	1,270	1,781
Gross carrying amount of Intangible assets	17,087	15,888
Accumulated amortization of Intangible assets	10,459	10,386
Total intangible assets	6,628	5,502
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	228	284
Accumulated amortization of Intangible assets (excluding MSRs)	0	0
Net carrying amount of Intangible assets (excluding MSRs)	228	284
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	8,396	7,606
Accumulated amortization of Intangible assets (excluding MSRs)	6,596	6,520
Net carrying amount of Intangible assets (excluding MSRs)	1,800	1,086
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	5,255	3,922
Accumulated amortization of Intangible assets (excluding MSRs)	2,249	2,021
Net carrying amount of Intangible assets (excluding MSRs)	3,006	1,901
Core deposit intangibles
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	854	1,050
Accumulated amortization of Intangible assets (excluding MSRs)	811	969
Net carrying amount of Intangible assets (excluding MSRs)	43	81
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	536	471
Accumulated amortization of Intangible assets (excluding MSRs)	298	252
Net carrying amount of Intangible assets (excluding MSRs)	238	219
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	33	37
Accumulated amortization of Intangible assets (excluding MSRs)	28	31
Net carrying amount of Intangible assets (excluding MSRs)	5	6
Other
Finite and Indefinite-lived Intangible Assets
Gross carrying amount of Intangible assets (excluding MSRs)	515	737
Accumulated amortization of Intangible assets (excluding MSRs)	477	593
Net carrying amount of Intangible assets (excluding MSRs)	$ 38	$ 144