Asset Quality - Concession Types for our Commercial Accruing and Nonaccruing TDRs (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Additional funds to borrowers related to lending related commitments	$ 32	$ 25
Interest rate reduction	104	177
Consumer accruing and nonaccruing TDRs [Member]
Interest rate reduction	$ 121	$ 62