Available-for-Sale and Held-to-Maturity Securities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Investment Holdings [Line Items]
FHLB, restricted stock holdings	$ 497		$ 497
Federal Reserve Bank, restricted stock holdings	347		345
Available-for-sale and other securities	15,207	[1]	15,362	[1]
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Investment Holdings [Line Items]
Available-for-sale and other securities	8,730	[2]	10,284	[2]
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises | InterestOnlyStripMember
Investment Holdings [Line Items]
Available-for-sale and other securities	$ 408		$ 110

[1] Amortized cost of $14,571 and $14,614 at December 31, 2012 and 2011, respectively.

[2] (a)        Includes interest-only mortgage backed securities of $408 and $110 as of December 31, 2012 and 2011, respectively, recorded at fair value with fair value changes recorded in securities gains, net and securities gains, net – non-qualifying hedges on mortgage servicing rights in the Consolidated Statements of Income.