Fair Value Disclosures (Notional or Contractual Amounts and Fair Values of Off-Balance Sheet Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Residential mortgage loans sold with recourse	$ 886	$ 1,019
Other loans sold with recourse	5,012	4,970
Letters of credit and financial guarantees written	5,012	5,164
Notional Or Contract Amount [Member]
Commitments to extend, originate or purchase credit	42,605	41,410
Residential mortgage loans sold with recourse	886	1,019
Other loans sold with recourse	5,012	4,970
Letters of credit and financial guarantees written	5,012	5,164
Fair Value [Member]
Commitments to extend, originate or purchase credit	78	74
Residential mortgage loans sold with recourse	12	12
Other loans sold with recourse	12	13
Letters of credit and financial guarantees written	$ 44	$ 30