Asset Quality (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Nonperforming Assets and Past Due Loans
Total nonperforming loans	$ 727	$ 1,068
Nonperforming loans held for sale	46	106
OREO	65	129
Other nonperforming assets	21	35
Total nonperforming assets	859	1,338
Restructured loans included in nonperforming loans	191	202
Restructured loans with a specifically allocated allowance	50	57
Specifically allocated allowance for restructured loans	10	18
Accruing loans past due 90 days or more	164	239
Accruing loans past due 30 through 89 days	$ 441	$ 476