Derivative Financial Instruments - Fair Value of Derivative Instruments Held For Other Purpose (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Other assets
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 1,496	[1]	$ 1,426	[1]
Other assets | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	801	[1]	901	[1]
Other assets | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	37	[1]	52	[1]
Other assets | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	653	[1]	472	[1]
Other assets | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	5	[1]	1	[1]
Interest taxes and other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	248	[1]	244	[1]
Interest taxes and other liabilities [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	90	[1]	97	[1]
Interest taxes and other liabilities [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	33	[1]	17	[1]
Interest taxes and other liabilities [Member] | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	116	[1]	126	[1]
Interest taxes and other liabilities [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	$ 9	[1]	$ 4	[1]

[1] 1) The derivative asset and derivative liabilities presented above may be eligible for netting and consequently may be shown net against a different line item on the consolidated balance sheet. Balance sheet categories in the above table represent the location of the assets and liabilities absent the netting of the balan