Available-for-Sale and Held-to-Maturity Securities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Investment Holdings
FHLB, restricted stock holdings	$ 249		$ 402
Federal Reserve Bank, restricted stock holdings	350		349
Available-for-sale and other securities	20,749	[1]	18,597	[1]
Interest-Only-Strip [Member]
Investment Holdings
Available-for-sale and other securities	$ 217		$ 262

[1] Amortized cost of $20,393 and $18,409 at March 31, 2014 and December 31, 2013, respectively.