Investment gains/losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairments	$ (19)	$ (85)
Investment gains/losses	1,131	505
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Gross gains from sales and other disposals	190	15
Gross losses from sales and other disposals	(29)	(54)
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Gross gains from sales and other disposals	1,004	109
Gross losses from sales and other disposals		(1)
Other Types of Investments [Member]
Gain (Loss) on Investments [Line Items]
Other investment gains/losses	(15)	521
Insurance and Other [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	1,059	434
Finance and Financial Products [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	$ 72	$ 71