Fair Value Disclosures (Notional or Contractual Amounts and Fair Values of Off-Balance Sheet Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Residential mortgage loans sold with recourse liability	$ 1,316	$ 1,624
Commitments to fund affordable housing investments	394	334
Notional/Contract amount [Member]
Commitments to extend, originate or purchase credit	40,249	36,917
Residential mortgage loans sold with recourse liability	1,316	1,624
Other loans sold with recourse	4,520	4,352
Letters of credit and financial guarantees written	6,095	7,291
Commitments to fund affordable housing investments	394	334
Fair value [Member]
Commitments to extend, originate or purchase credit	71	65
Residential mortgage loans sold with recourse liability	6	6
Other loans sold with recourse	15	19
Letters of credit and financial guarantees written	27	41
Commitments to fund affordable housing investments	$ 386	$ 316