Fair Value (Fair Value Measurements - Recurring Fair Value Inputs) (Details) (USD $) In Millions, unless otherwise specified								12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2011 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Retained Interest [Member] Discounted cash flow [Member] Minimum [Member]	Dec. 31, 2012 Retained Interest [Member] Discounted cash flow [Member] Maximum [Member]
Fair value inputs, Quantitative Information [Line Items]
Mortgage servicing rights	$ 952	$ 2,519	$ 3,738	$ 952	$ 2,519	$ 952	$ 2,519
Fair Value Inputs, Discount Rate								5.40%	6.10%
Retained Interest, Fair Value Disclosure	$ 154	$ 231		$ 154	$ 231	$ 154	$ 231
Fair Value Inputs, Commercial Paper Rate								0.00%	0.10%

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the interests continued to be held by a transferor (retained or residual interest) after transferring financial assets to a third party.

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Fair value as of the balance sheet date of an asset representing net future revenues from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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