Trading Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Derivatives included in trading assets, amount offset	[1],[2]	$ 4,678	$ 4,811
Derivatives included in trading liabilities, amount offset	[1],[2]	1,021	1,724
Trading Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Derivatives included in trading assets, amount offset		4,678	4,811
Trading Liabilities [Member]
Schedule of Available-for-sale Securities [Line Items]
Derivatives included in trading liabilities, amount offset		$ 1,021	$ 1,724

[1] Netting is performed at a counterparty level in cases where enforceable master netting and credit support agreements are in place, regardless of the type of derivative instrument. Therefore, we have not attempted to allocate netting to the different types of derivative instruments shown in the table above.

[2] Represents the netting of cash collateral posted and received by counterparty under enforceable credit support agreements.