Fair Value (Fair Value Option Gains Losses for Mortgage Loans Held-for-Sale) (Details) (Mortgage Loans Held-for-sale [Member], Other Revenues [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Mortgage Loans Held-for-sale [Member] | Other Revenues [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Instrument-specific credit risk based on changes in credit spreads for non-agency loans and adjustments in individual loan quality	$ 0	$ (2)	$ 0	$ 0
Other changes in estimated fair value	0	(27)	0	71
Total gains (losses) recognized in other revenues	$ 0	$ (29)	$ 0	$ 71