Derivative contracts - gains and losses (Detail) (Finance and Financial Products [Member], USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Derivative contracts gains and losses [Line Items]
Derivative gains/losses	$ (2,443)	$ (146)	$ (2,356)	$ (1,911)
Credit default contracts [Member]
Derivative contracts gains and losses [Line Items]
Derivative gains/losses	(247)	519	(35)	407
Equity index put options [Member]
Derivative contracts gains and losses [Line Items]
Derivative gains/losses	(2,089)	(700)	(2,137)	(2,319)
Other [Member]
Derivative contracts gains and losses [Line Items]
Derivative gains/losses	$ (107)	$ 35	$ (184)	$ 1