Available-for-Sale and Held-to-Maturity Securities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 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	22,814	[1]	18,597	[1]
Interest-Only-Strip [Member]
Investment Holdings
Available-for-sale and other securities	201		262
Agency Commercial Mortgage Backed Securities
Investment Holdings
Available-for-sale and other securities	3,051
Non-agency Commercial Mortgage Backed Securities
Investment Holdings
Available-for-sale and other securities	1,586		1,368
Asset Backed Securities
Investment Holdings
Available-for-sale and other securities	$ 1,225		$ 1,400

[1] Amortized cost of $22,184 and $18,409 at June 30, 2014 and December 31, 2013, respectively.