Derivative Financial Instruments - Fair Value of Derivative Instruments Held For Other Purpose (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Derivative Liabilities	$ (85,543)	$ (86,546)
Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	1,566	1,021
Other assets [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	986	957
Other assets [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	33	11
Other assets [Member] | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	546	51
Other assets [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets	1	2
Interest taxes and other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	256	214
Interest taxes and other liabilities [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	113	106
Interest taxes and other liabilities [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	31	13
Interest taxes and other liabilities [Member] | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	107	87
Interest taxes and other liabilities [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	$ 5	$ 8