Goodwill and Other Intangible Assets - Other Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Intangible Assets By Major Class [Line Items]
Increase (decrease) in other intangible assets	$ (426)
Amortization of intangibles	380	637	957
Components of credit card relationships, core deposits and other intangible assets [Abstract]
Gross amount	3,391	10,589
Accumulated amortization	2,199	8,971
Net carrying value	1,192	1,618
Indefinite-lived intangible assets	600	600
Purchased credit card relationships
Intangible Assets By Major Class [Line Items]
Amortization of intangibles	97	195	309
Components of credit card relationships, core deposits and other intangible assets [Abstract]
Gross amount	200	3,540
Accumulated amortization	166	3,409
Net carrying value	34	131
Other credit card-related intangibles
Intangible Assets By Major Class [Line Items]
Amortization of intangibles	51	58	265
Components of credit card relationships, core deposits and other intangible assets [Abstract]
Gross amount	497	542
Accumulated amortization	378	369
Net carrying value	119	173
Core deposit intangibles
Intangible Assets By Major Class [Line Items]
Amortization of intangibles	102	196	239
Components of credit card relationships, core deposits and other intangible assets [Abstract]
Gross amount	814	4,133
Accumulated amortization	757	3,974
Net carrying value	57	159
Other intangibles
Intangible Assets By Major Class [Line Items]
Amortization of intangibles	130	188	144
Components of credit card relationships, core deposits and other intangible assets [Abstract]
Gross amount	1,880	2,374
Accumulated amortization	898	1,219
Net carrying value	$ 982	$ 1,155