Loan Servicing (Analysis of Activity in Residential Mortgage Servicing Rights) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011
Loan Servicing [Abstract]
Carrying value, beginning balance	$ 563		$ 830
Additions	195		165
Fair value changes from valuation inputs or assumptions	(67)		(319)
Other changes	(128)	[1]	(103)	[1]
Carrying value, ending balance	$ 563		$ 573

[1] Represents the realization of expected net servicing cash flows, expected borrower payments and the passage of time.