Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 832,792	$ 747,508	$ 724,177
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 344,355	294,979	$ 288,449
Period past due, credit analysis factors, charge off criteria	90 days
Consumer, excluding credit card | 30 or more days past due
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 | Junior lien
Loans and Leases Receivable Disclosure [Line Items]
Period past due, credit analysis factors, charge off criteria	180 days
Consumer, excluding credit card | Home equity | Residential real estate - PCI
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 14,989	17,095
Consumer, excluding credit card | Home equity | Senior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	14,848	16,367
Consumer, excluding credit card | Home equity | Senior lien | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	332	362
Consumer, excluding credit card | Home equity | Junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	30,711	36,375
Consumer, excluding credit card | Home equity | Junior lien | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	220	267
Consumer, excluding credit card | Home equity | Junior lien | Residential real estate - PCI
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	11,834	13,851
Consumer, excluding credit card | Mortgages | Prime, including option ARMs
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	162,549	104,921
Consumer, excluding credit card | Mortgages | Prime, including option ARMs | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	5,560	6,879
Consumer, excluding credit card | Mortgages | Prime, including option ARMs | Residential real estate - PCI
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	8,893	10,220
Consumer, excluding credit card | Mortgages | Subprime
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	3,690	5,056
Consumer, excluding credit card | Mortgages | Subprime | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	174	271
Consumer, excluding credit card | Mortgages | Subprime | Residential real estate - PCI
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	3,263	3,673
Consumer, excluding credit card | Mortgages | Option ARMs | Residential real estate - PCI
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	13,853	15,708
Consumer, excluding credit card | Residential real estate
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 211,798	162,719
Consumer, excluding credit card | Residential real estate | Refreshed FICO scores less than 660
Loans and Leases Receivable Disclosure [Line Items]
Low FICO score (or below)	660
Consumer, excluding credit card | Residential real estate | 150 days past due
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 6,286	7,779
Consumer, excluding credit card | Residential real estate | Residential real estate - PCI
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	40,998	46,696
Consumer, excluding credit card | Auto
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	60,255	54,536
Consumer, excluding credit card | Business banking
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	21,208	20,058
Consumer, excluding credit card | Student and other
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 10,096	$ 10,970