Trading Assets and Liabilities - Additional Information (Detail) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivatives included in trading assets, amount offset	[1],[2]	$ 5,473	$ 4,942
Derivatives included in trading liabilities, amount offset	[1],[2]	1,305	1,530
Trading Assets [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivatives included in trading assets, amount offset		4,463	4,652
Trading Liabilities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivatives included in trading liabilities, amount offset		$ 1,305	$ 1,530

[1] Netting is performed at a counterparty level in cases where enforceable master netting 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 netting agreements.