Loan Servicing (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Total residential mortgage servicing portfolio	$ 94,600,000,000		$ 91,600,000,000
Unpaid principal balances of residential mortgage loans serviced for others	70,300,000,000		67,100,000,000
Unpaid principal balance of mortgage loans sold	7,600,000,000	5,500,000,000
Recognized pre-tax gains on mortgage loans sold	127,000,000	35,000,000
Approximate weighted average servicing fee	0.33%	0.35%
Weighted average coupon interest rate on the portfolio of mortgage loans serviced for others	4.89%	5.17%
Recognized servicing fees	60,000,000	58,000,000
Residential mortgage loans sold with recourse liability	1,228,000,000		1,316,000,000
Maximum recourse exposure	502,000,000		522,000,000
Reserves related to residential mortgage loans recourse exposures	6,000,000		6,000,000
Reserves related to potential losses resulting from repurchases of mortgage loans sold to government-sponsored entities	39,000,000		29,000,000
Origination of commercial real estate mortgages	1,300,000,000	930,000,000
Unpaid principal balances of commercial mortgage loans serviced for others	25,800,000,000		25,400,000,000
Commercial mortgage loans serviced for others that were covered by recourse provisions	4,751,000,000		4,520,000,000
Maximum exposure to loss for commercial mortgage loans serviced for others that were covered by recourse provisions	1,300,000,000		1,200,000,000
Reserves related to commercial mortgage loans recourse exposures	$ 16,000,000		$ 15,000,000