Goodwill and Intangible Assets - Amortization Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 213us-gaap_AmortizationOfIntangibleAssets	$ 239us-gaap_AmortizationOfIntangibleAssets
Purchased credit card and Affinity relationships
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	89	105
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	32	36
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	87	91
Other intangibles
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 5	$ 7