Loans - Consumer, Excluding Credit Card Loans (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 756,971,000,000	$ 747,508,000,000	$ 721,160,000,000
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	304,917,000,000	294,979,000,000	287,930,000,000
Consumer, excluding credit card | Home equity - senior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	15,922,000,000	16,367,000,000
Consumer, excluding credit card | Home equity - junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	34,968,000,000	36,375,000,000
Consumer, excluding credit card | Mortgages - prime, including option ARMS
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	117,275,000,000	104,921,000,000
Consumer, excluding credit card | Mortgages - subprime
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	4,826,000,000	5,056,000,000
Consumer, excluding credit card | Auto
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	55,455,000,000	54,536,000,000
Consumer, excluding credit card | Business banking
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	20,375,000,000	20,058,000,000
Consumer, excluding credit card | Student and other
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	10,740,000,000	10,970,000,000
Consumer, excluding credit card | Purchased Credit-Impaired, Home Equity
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	16,638,000,000	17,095,000,000
Consumer, excluding credit card | Purchased Credit-Impaired, Prime Mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	9,916,000,000	10,220,000,000
Consumer, excluding credit card | Purchased Credit-Impaired, Subprime Mortgage
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	3,559,000,000	3,673,000,000
Consumer, excluding credit card | Purchased Credit-Impaired, Option ARMs
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 15,243,000,000	$ 15,708,000,000