Fair Value Disclosures (Notional or Contractual Amounts and Fair Values of Off-Balance Sheet Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Residential mortgage loans sold with recourse	$ 1,085	$ 1,316
Other loans sold with recourse	4,847	4,520
Letters of credit and financial guarantees written	5,564	6,095
Notional/Contract amount [Member]
Commitments to extend, originate or purchase credit	44,579	40,249
Residential mortgage loans sold with recourse	1,085	1,316
Other loans sold with recourse	4,847	4,520
Letters of credit and financial guarantees written	5,564	6,095
Fair Value [Member]
Commitments to extend, originate or purchase credit	82	71
Residential mortgage loans sold with recourse	12	6
Other loans sold with recourse	14	15
Letters of credit and financial guarantees written	$ 36	$ 27