Loans - Consumer, Excluding Credit Card Loans, PCI Delinquency Statistics (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 747,508	$ 724,177	$ 726,835
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	294,979	288,449	292,620
Consumer, excluding credit card | Purchased Credit-Impaired, Home Equity Senior Lien
Loans and Leases Receivable Disclosure [Line Items]
Percentage of senior liens to total financing receivables	20.00%
Consumer, excluding credit card | Purchased Credit-Impaired, Home Equity Junior Lien, Excluding Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	736	908
Total 30 plus day delinquency rate	8.83%	8.15%
Consumer, excluding credit card | Purchased Credit-Impaired, Home Equity Junior Lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	13,851	15,914
Total 30 plus day delinquency rate	6.55%	6.84%
Consumer, excluding credit card | HELOC, Within the revolving period | Purchased Credit-Impaired, Home Equity Junior Lien, Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	8,972	12,670
Total 30 plus day delinquency rate	6.42%	6.76%
Home equity line of credit, open-ended revolving period	10 years
Consumer, excluding credit card | HELOCs, Beyond the revolving period | Purchased Credit-Impaired, Home Equity Junior Lien, Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	4,143	2,336
Total 30 plus day delinquency rate	6.42%	6.72%
Consumer, excluding credit card | 30–89 days past due | Purchased Credit-Impaired, Home Equity Junior Lien, Excluding Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	20	24
Consumer, excluding credit card | 30–89 days past due | Purchased Credit-Impaired, Home Equity Junior Lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	251	321
Consumer, excluding credit card | 30–89 days past due | HELOC, Within the revolving period | Purchased Credit-Impaired, Home Equity Junior Lien, Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	155	243
Consumer, excluding credit card | 30–89 days past due | HELOCs, Beyond the revolving period | Purchased Credit-Impaired, Home Equity Junior Lien, Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	76	54
Consumer, excluding credit card | 90–149 days past due | Purchased Credit-Impaired, Home Equity Junior Lien, Excluding Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	7	11
Consumer, excluding credit card | 90–149 days past due | Purchased Credit-Impaired, Home Equity Junior Lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	81	120
Consumer, excluding credit card | 90–149 days past due | HELOC, Within the revolving period | Purchased Credit-Impaired, Home Equity Junior Lien, Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	50	88
Consumer, excluding credit card | 90–149 days past due | HELOCs, Beyond the revolving period | Purchased Credit-Impaired, Home Equity Junior Lien, Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	24	21
Consumer, excluding credit card | 150 days past due | Purchased Credit-Impaired, Home Equity Junior Lien, Excluding Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	38	39
Consumer, excluding credit card | 150 days past due | Purchased Credit-Impaired, Home Equity Junior Lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	575	647
Consumer, excluding credit card | 150 days past due | HELOC, Within the revolving period | Purchased Credit-Impaired, Home Equity Junior Lien, Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	371	526
Consumer, excluding credit card | 150 days past due | HELOCs, Beyond the revolving period | Purchased Credit-Impaired, Home Equity Junior Lien, Lines of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 166	$ 82