Loan Servicing (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Total residential mortgage servicing portfolio	$ 91,600,000,000	$ 83,500,000,000	$ 73,700,000,000
Unpaid principal balances of residential mortgage loans serviced for others	67,100,000,000	61,800,000,000	54,600,000,000
Mortgage loans with unpaid principal balances, sold	17,200,000,000	19,100,000,000	25,800,000,000
Recognized pre-tax gains on mortgage loans sold	175,000,000	235,000,000	357,000,000
Approximate weighted average servicing fee	0.34%	0.35%	0.37%
Weighted average coupon interest rate on the portfolio of mortgage loans serviced for others	5.02%	5.26%	5.57%
Recognized servicing fees	240,000,000	226,000,000	190,000,000
Residential mortgage loans sold with recourse liability	1,316,000,000	1,624,000,000
Maximum recourse exposure	522,000,000	597,000,000
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	29,000,000	15,000,000
Reduction in the value of residential mortgage servicing rights due to revised servicing cost assumptions	30,000,000
Reduction in the value of residential mortgage servicing rights due to revised prepayment speed assumptions	293,000,000
Origination of commercial real estate mortgages	4,800,000,000	3,100,000,000	2,300,000,000
Unpaid principal balances of commercial mortgage loans serviced for others	25,400,000,000	24,100,000,000	24,300,000,000
Commercial mortgage loans serviced for others that were covered by recourse provisions	4,500,000,000	4,400,000,000
Maximum exposure to loss for commercial mortgage loans serviced for others that were covered by recourse provisions	1,200,000,000	1,200,000,000
Reserves related to commercial mortgage loans recourse exposures	15,000,000	19,000,000
Commercial mortgage servicing rights at amortized cost	$ 107,000,000	$ 103,000,000