Fair Value Disclosures (Notional or Contractual Amounts and Fair Values of Off-Balance Sheet Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Residential mortgage loans sold with recourse	$ 649	$ 667
Other loans sold with recourse	4,235	4,264
Letters of credit and financial guarantees	3,422	3,462
Notional Or Contract Amount [Member]
Commitments to extend, originate or purchase credit	51,588	49,333
Residential mortgage loans sold with recourse	649	667
Other loans sold with recourse	4,235	4,264
Letters of credit and financial guarantees	3,422	3,462
Fair Value [Member]
Commitments to extend, originate or purchase credit	104	97
Residential mortgage loans sold with recourse	9	9
Other loans sold with recourse	7	7
Letters of credit and financial guarantees	$ 24	$ 22