Asset Quality (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Nonperforming Assets and Past Due Loans
Total nonperforming loans	$ 666	$ 727	$ 885
Nonperforming loans held for sale	24	46	86
OREO	61	65	97
Other nonperforming assets	16	21	21
Total nonperforming assets	767	859	1,089
Restructured loans included in nonperforming loans	184	191	136
Restructured loans with an allocated specific allowance (b)	47	50	29
Specifically allocated allowance for restructured loans (c)	18	10	9
Accruing loans past due 90 days or more	169	164	153
Accruing loans past due 30 through 89 days	$ 420	$ 441	$ 474