Investment gains/losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Gain (Loss) on Investments [Line Items]
OTTI losses	$ (143)		$ (228)	$ (337)
Investment gains/losses	1,714	917	2,711	936
Insurance and Other [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	1,640	725	2,529	720
Finance and Financial Products [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	74	192	182	216
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Gross gains from sales and other disposals	727	77	809	168
Gross losses from sales and other disposals	(55)		(147)	(345)
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Gross gains from sales and other disposals	548	645	918	1,218
Gross losses from sales and other disposals	(37)	(4)	(57)	(11)
Other Types Of Investments [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	$ 674	$ 199	$ 1,416	$ 243