Investment gains/losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairments			$ (19)	$ (85)
Investment gains/losses	2,366	492	3,497	997
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Gross gains from sales and other disposals	39	67	229	82
Gross losses from sales and other disposals	(19)	(38)	(48)	(92)
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Gross gains from sales and other disposals	2,391	261	3,395	370
Gross losses from sales and other disposals	(3)	(19)	(3)	(20)
Other Types of Investments [Member]
Gain (Loss) on Investments [Line Items]
Other investment gains/losses	(42)	221	(57)	742
Insurance and Other [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	2,366	455	3,425	889
Finance and Financial Products [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses		$ 37	$ 72	$ 108