Loan Servicing (Residential Mortgage Servicing Rights Sensitivity) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 Yr
Weighted average life, in years	7.1
Residential Mortgage Servicing Rights [Member]
Weighted Average Prepayment speed	8.70%
Effect on fair value of a 10% increase in weighted average prepayment speed	$ (32)
Effect on fair value of a 20% increase in weighted average prepayment speed	(63)
Weighted average OAS	9.70%
Effect on fair value of a 10% increase in weighted average OAS	(33)
Effect on fair value of a 20% increase in weighted average OAS	$ (63)
Composition of residential mortgage loans serviced for others	100.00%
Residential Mortgage Servicing Rights [Member] | Maximum [Member]
Weighted Average Prepayment speed	11.90%
Weighted average OAS	10.20%
Residential Mortgage Servicing Rights [Member] | Minimum [Member]
Weighted Average Prepayment speed	6.90%
Weighted average OAS	9.50%
Fixed-Rate Residential Mortgage [Member]
Composition of residential mortgage loans serviced for others	99.60%
Adjustable Rate Residential Mortgage [Member]
Composition of residential mortgage loans serviced for others	0.40%