Loans - Consumer, Excluding Credit Card Loans (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
Low FICO Score	660
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	294,979	288,449	292,620
Consumer, excluding credit card | Days Past Due, 30 or More
Loans and Leases Receivable Disclosure [Line Items]
Period past due, credit analysis factors, charge off criteria	30 days
Consumer, excluding credit card | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Period past due, credit analysis factors, charge off criteria	150 days
Consumer, excluding credit card | Home equity - senior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	16,367	17,113
Consumer, excluding credit card | Home equity - senior lien | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	362	345
Consumer, excluding credit card | Home equity - junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	36,375	40,750
Period past due, credit analysis factors, charge off criteria	180 days
Consumer, excluding credit card | Home equity - junior lien | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	267	224
Consumer, excluding credit card | Mortgages - prime, including option ARMS
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	104,921	87,162
Consumer, excluding credit card | Mortgages - prime, including option ARMS | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	6,879	7,899
Consumer, excluding credit card | Mortgages - subprime
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	5,056	7,104
Consumer, excluding credit card | Mortgages - subprime | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	271	502
Consumer, excluding credit card | Auto
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	54,536	52,757
Consumer, excluding credit card | Business banking
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	20,058	18,951
Consumer, excluding credit card | Student and other
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	10,970	11,557
Consumer, excluding credit card | Purchased Credit-Impaired, Home Equity
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	17,095	18,927
Consumer, excluding credit card | Purchased Credit-Impaired, Prime Mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	10,220	12,038
Consumer, excluding credit card | Purchased Credit-Impaired, Subprime Mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	3,673	4,175
Consumer, excluding credit card | Purchased Credit-Impaired, Option ARMs
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 15,708	$ 17,915