Fair Value, Option, Instrument Specific Credit Risk (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) attributable to instrument-specific credit risk	$ 35	$ 51	$ 67	$ 73
Trading assets - loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) attributable to instrument-specific credit risk	4	6	19	18
Mortgages held for sale [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains (losses) attributable to instrument-specific credit risk	$ 31	$ 45	$ 48	$ 55