Asset Quality (Home Equity and Residential Real Estate Balances) (Details) - USD ($) $ in Millions	Mar. 31, 2016		Dec. 31, 2015		Mar. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Purchased Impaired Loans - Outstanding Balance	$ 3,743		$ 3,933
Total loans	207,485	[1]	206,696	[1]	$ 204,722
Total home equity and residential real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans - Excluding Purchased Impaired Loans	42,007		42,268
Purchased Impaired Loans - Outstanding Balance	3,537		3,684
Government insured or guaranteed residential real estate mortgages	892		923
Difference between outstanding balance and recorded investment - purchased impaired loans	(306)		(331)
Total loans	$ 46,130		$ 46,544

[1] Our consolidated assets at March 31, 2016 included the following for which we have elected the fair value option: Federal funds sold and resale agreements of $138 million, Loans held for sale of $1.4 billion, Loans of $.9 billion, and Other assets of $375 million. Our consolidated assets at December 31, 2015 included the following for which we have elected the fair value option: Federal funds sold and resale agreements of $137 million, Loans held for sale of $1.5 billion, Loans of $.9 billion, and Other assets of $521 million.