Derivative contracts - gains and losses (Detail) (Finance and Financial Products [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains/losses	$ 155	$ 461	$ 391	$ 1,667
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains/losses	155	461	391	1,667
Not Designated as Hedging Instrument [Member] | Equity Index Put Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains/losses	65	390	(67)	1,636
Not Designated as Hedging Instrument [Member] | Credit Default Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains/losses	84	99	457	85
Not Designated as Hedging Instrument [Member] | Other, principally interest rate and foreign currency [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains/losses	$ 6	$ (28)	$ 1	$ (54)