Financial Instruments (Net investment hedges in foreign operations) (Details) (Net Investment Hedge [Member], USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Foreign Exchange Contract [Member]	Mar. 31, 2011 Foreign Exchange Contract [Member]
Net investment hedges in foreign operation
Gain (loss) recognized in AOCI			$ (1,502)	$ (801)
Gain (loss) reclassified from AOCI into earnings			(10)	(338)
Hedge ineffectiveness gain (loss)	$ (220)	$ (278)