Loans - Consumer, Excluding Credit Card Loans (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 779,705	$ 747,508	$ 735,369
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	316,781	294,979	$ 288,214
Consumer, excluding credit card | Home equity - senior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	15,541	16,367
Consumer, excluding credit card | Home equity - junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	33,434	36,375
Consumer, excluding credit card | Mortgages - prime, including option ARMS
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	132,556	104,921
Consumer, excluding credit card | Mortgages - subprime
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	3,976	5,056
Consumer, excluding credit card | Auto
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	56,330	54,536
Consumer, excluding credit card | Business banking
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	20,564	20,058
Consumer, excluding credit card | Student and other
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	10,574	10,970
Consumer, excluding credit card | Purchased Credit-Impaired, Home Equity
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	16,088	17,095
Consumer, excluding credit card | Purchased Credit-Impaired, Prime Mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	9,553	10,220
Consumer, excluding credit card | Purchased Credit-Impaired, Subprime Mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	3,449	3,673
Consumer, excluding credit card | Purchased Credit-Impaired, Option ARMs
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 14,716	$ 15,708