Asset Quality - Nonperforming Assets and Past Due Loans (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Disclosure Loans Classified As Nonperforming [Abstract]
Total nonperforming loans	$ 650	$ 674	$ 666
Nonperforming loans held for sale	23	25	24
OREO	21	22	61
Other nonperforming assets	11	14	16
Total nonperforming assets	705	735	767
Nonperforming assets from discontinued operations - education lending	15	20	19
Restructured loans included in nonperforming loans	178	249	184
Restructured loans with an allocated specific allowance	52	114	47
Specifically allocated allowance for restructured loans	30	33	18
Accruing loans past due 90 days or more	83	78	169
Accruing loans past due 30 through 89 days	$ 368	$ 424	$ 420