Investment Securities (Investment Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Available-for-sale Securities [Abstract]
Taxable interest	$ 67	$ 96	$ 225	$ 294
Taxable dividends	6	6	18	17
Total interest and dividends on available-for-sale securities	$ 73	$ 102	$ 243	$ 311