Trading Assets and Liabilities - Trading Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	$ 27,448		$ 35,995
Trading liabilities	15,337		19,820
U.S. Treasury [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	1,530		2,484
US Government Agencies Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	73		337
US Government sponsored enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	124	[1]	32	[1]
Asset backed securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	469		687
Corporate and foreign bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	6,830	[2]	9,583	[2]
Other securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	24		36
Precious metals [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	9,397		12,332
Trading liabilities	4,545		5,767
Derivatives [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	9,001		10,504
Trading liabilities	10,301		13,846
Securities sold, not yet purchased [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading liabilities	$ 491		$ 207

[1] Includes mortgage backed securities of $97 million and $16 million issued or guaranteed by the Federal National Mortgage Association (“FNMA”) and $27 million and $16 million issued or guaranteed by the Federal Home Loan Mortgage Corporation (“FHLMC”) at June 30, 2013 and December 31, 2012, respectively.

[2] We did not hold any foreign bonds issued by the governments of Greece, Ireland, Italy, Portugal or Spain at either June 30, 2013 or December 31, 2012.