Trading Assets and Liabilities - Trading Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	$ 25,527		$ 30,874
Trading liabilities	11,065		14,699
U.S. Treasury [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	2,064		2,484
US Government Agencies Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	330		337
US Government sponsored enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	161	[1]	32	[1]
Obligations of U.S. states and political subdivision [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	16		0
Asset backed securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	482		687
Corporate and foreign bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	7,277	[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	10,587		12,332
Trading liabilities	3,549		5,767
Derivatives [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading assets	4,586		5,383
Trading liabilities	6,595		8,725
Securities sold, not yet purchased [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading liabilities	$ 921		$ 207

[1] Includes mortgage backed securities of $134 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 September 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 September 30, 2013 or December 31, 2012.