Trading Assets and Liabilities - Additional Information (Detail) (USD $)	Sep. 30, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Fair value of derivatives reduced by cash collateral received	$ 4,491,000,000	[1],[2]	$ 5,123,000,000	[1],[2]
Trading Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value of derivatives reduced by cash collateral received	4,500,000,000		5,100,000,000
Trading Liabilities [Member]
Schedule of Available-for-sale Securities [Line Items]
Right to reclaim cash	$ 2,100,000,000		$ 1,300,000,000

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

[2] 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.