Asset Quality - Nonperforming Assets and Past Due Loans (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Receivables [Abstract]
Total nonperforming loans	$ 541	$ 674	$ 653
Nonperforming loans held for sale	13	25	19
OREO	15	22	29
Other nonperforming assets	10	14	17
Total nonperforming assets	579	735	718
Nonperforming assets from discontinued operations - education lending	23	20	22
Restructured loans included in nonperforming loans	228	249	217
Restructured loans with an allocated specific allowance	104	114	78
Specifically allocated allowance for restructured loans	46	33	31
Accruing loans past due 90 days or more	90	78	89
Accruing loans past due 30 through 89 days	$ 288	$ 424	$ 354