Asset Quality - Post-Modification Outstanding Recorded Investment by Concession Type for Our Commercial Accruing and Nonaccruing TDRs (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Noncancelable Obligations Future Minimum Payments Due [Line Items]
Total commercial and consumer TDRs	$ 270	$ 338
Total Loans	57,381	54,457
Commercial Loans [Member]
Noncancelable Obligations Future Minimum Payments Due [Line Items]
Interest rate reduction	13	95
Forgiveness of principal	2	5
Other	25	7
Total	40	107
Consumer Loans [Member]
Noncancelable Obligations Future Minimum Payments Due [Line Items]
Interest rate reduction	140	130
Forgiveness of principal	4	5
Other	86	96
Total	$ 230	$ 231