Goodwill and Other Intangible Assets (Commercial and Residential Mortgage Loan Servicing Assets - Key Valuation Assumptions) (Details) (Servicing Contracts [Member], USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Commercial Real Estate [Member]
Sensitivity Analysis Of Fair Value Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities Impact Of Adverse Change In Assumption [Line Items]
Fair Value	$ 530	$ 427
Weighted-average life	5 years 6 months	5 years 5 months
Weighted-average constant prepayment rate	6.60%	7.63%
Decline in fair value from 10% adverse change in prepayment rate	10	8
Decline in fair value from 20% adverse change in prepayment rate	19	16
Effective Discount Rate	7.06%	7.70%
Decline in fair value from 10% adverse change in interest rate	13	12
Decline in fair value from 20% adverse change in interest rate	27	23
Residential Mortgages [Member]
Sensitivity Analysis Of Fair Value Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities Impact Of Adverse Change In Assumption [Line Items]
Fair Value	975	650
Weighted-average life	6 years 11 months	4 years 4 months
Weighted-average constant prepayment rate	10.13%	18.78%
Decline in fair value from 10% adverse change in prepayment rate	38	45
Decline in fair value from 20% adverse change in prepayment rate	74	85
Residential Mortgages [Member] | Weighted Average Option Adjusted Spread [Member]
Sensitivity Analysis Of Fair Value Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities Impact Of Adverse Change In Assumption [Line Items]
Decline in fair value from 10% adverse change in interest rate	42	26
Decline in fair value from 20% adverse change in interest rate	$ 80	$ 49
Other assumptions or inputs	10.96%	11.15%