Loans and Allowance for Credit Losses, Significant Activity (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
Loans and Allowance for Credit Losses, Significant Activity [Abstract]
Purchases	$ 1,021	$ 2,858	$ 10,363	$ 4,964
Sales	(960)	(2,027)	(4,218)	(4,807)
Transfers to mortgages/loans held for sale	(46)	(54)	(69)	(274)
Total Commercial [Member]
Loans and Allowance for Credit Losses, Significant Activity [Abstract]
Purchases	1,021	2,575	10,196	4,681
Sales	(796)	(1,648)	(3,731)	(4,114)
Transfers to mortgages/loans held for sale	(41)	(35)	(59)	(205)
Total Consumer [Member]
Loans and Allowance for Credit Losses, Significant Activity [Abstract]
Purchases	0	283	167	283
Sales	(164)	(379)	(487)	(693)
Transfers to mortgages/loans held for sale	$ (5)	$ (19)	$ (10)	$ (69)