Derivative Instruments and Other Financial Instruments Used For Hedging - Notional Amounts, Balance Sheet Location and Fair Value Amounts of Derivative Instruments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	$ 60,709	$ 60,118
Asset Derivatives, Fair Value	1,144	1,443
Liability Derivatives, Fair Value	1,011	1,320
Trading derivatives
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	58,533	51,609
Asset Derivatives, Fair Value	1,141	1,414
Liability Derivatives, Fair Value	999	1,317
Derivatives designated as other than trading
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	2,176	8,509
Asset Derivatives, Fair Value	3	29
Liability Derivatives, Fair Value	12	3
Interest rate derivative contracts [Member] | Trading derivatives
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	43,941	37,790
Asset Derivatives, Fair Value	793	1,075
Liability Derivatives, Fair Value	697	1,009
Interest rate derivative contracts [Member] | Designated as hedging instrument [Member] | Derivatives designated as other than trading
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	2,000	8,400
Asset Derivatives, Fair Value	1	28
Liability Derivatives, Fair Value	7
Commodity derivative contracts [Member] | Trading derivatives
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	6,249	5,595
Asset Derivatives, Fair Value	118	167
Liability Derivatives, Fair Value	106	140
Foreign exchange derivative contracts [Member] | Trading derivatives
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	4,597	4,593
Asset Derivatives, Fair Value	63	69
Liability Derivatives, Fair Value	28	65
Equity Derivative contracts [Member] | Trading derivatives
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	3,746	3,631
Asset Derivatives, Fair Value	167	103
Liability Derivatives, Fair Value	168	103
Other contracts [Member] | Not designated as hedging instruments [Member] | Derivatives designated as other than trading
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	176	109
Asset Derivatives, Fair Value	2	1
Liability Derivatives, Fair Value	$ 5	$ 3