Shareholders' Equity (Adjustments to Accumulated Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Class of Stock [Line Items]
Net interest revenue	$ 576	$ 625
Total reclassifications out of AOCI	455	417
Reclassification out of Accumulated Other Comprehensive Income [Member]
Class of Stock [Line Items]
Total reclassifications out of AOCI	5
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges | Interest-rate contracts | Reclassification out of Accumulated Other Comprehensive Income [Member]
Class of Stock [Line Items]
Net interest revenue	1
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income [Member]
Class of Stock [Line Items]
Net gains (losses) from sales of available-for-sale securities	(3)
Net realized gains from sales of available-for-sale securities, tax	2
Accumulated Other-than-Temporary Impairment | Reclassification out of Accumulated Other Comprehensive Income [Member]
Class of Stock [Line Items]
Losses reclassified (from) to other comprehensive income	2
Other-than-temporary impairment on held-to-maturity securities related to factors other than credit, tax	1
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income [Member]
Class of Stock [Line Items]
Compensation and employee benefits expense	5
Amortization of actuarial losses, tax	$ 3