Loan Servicing (Analysis of Activity in Residential Mortgage Servicing Rights) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Loan Servicing [Abstract]
Carrying value, beginning balance	$ 563		$ 830
Additions	84		86
Fair value changes from valuation inputs or assumptions	92		40
Other changes	(43)	[1]	(28)	[1]
Carrying value, ending balance	$ 696		$ 928

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