Investment gains/losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairments	$ (678)	$ (143)	$ (697)	$ (228)
Investment gains/losses	(376)	1,714	3,121	2,711
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Gross gains from sales and other disposals	4	727	233	809
Gross losses from sales and other disposals	(25)	(55)	(73)	(147)
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Gross gains from sales and other disposals	354	548	3,749	918
Gross losses from sales and other disposals	(38)	(37)	(41)	(57)
Other Types of Investments [Member]
Gain (Loss) on Investments [Line Items]
Other investment gains/losses	7	674	(50)	1,416
Insurance and Other [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	(376)	1,640	3,049	2,529
Finance and Financial Products [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses		$ 74	$ 72	$ 182

- Definition

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

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