Asset Quality - Nonperforming Assets and Past Due Loans (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Receivables [Abstract]
Total nonperforming loans	$ 437	$ 418	$ 449
Nonperforming loans held for sale			1
OREO	20	18	12
Other nonperforming assets			7
Total nonperforming assets	457	436	469
Nonperforming assets from discontinued operations-education lending	8	11	20
Restructured loans included in nonperforming loans	141	157	178
Restructured loans with an allocated specific allowance	70	82	51
Specifically allocated allowance for restructured loans	39	34	32
Accruing loans past due 90 days or more	111	96	89
Accruing loans past due 30 through 89 days	$ 216	$ 235	$ 267