Losses associated with the earthquake in Japan (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		19 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012
Operating income (loss)	$ 840	$ 814	$ 1,834	$ 2,627
Revenue	3,390	3,466	9,846	10,315
Earthquake in Japan, March 11, 2011 [Member]
Operating income (loss)				(98)	(101)
Insurance Settlement, Property Damage Claims [Member] | Earthquake in Japan, March 11, 2011 [Member]
Operating income (loss)	10	13	13	20	36
Insurance Settlement, Business Interruption Claims [Member] | Earthquake in Japan, March 11, 2011 [Member]
Revenue	$ 60	$ 22	$ 135	$ 22	$ 172