Quarterly financial data (unaudited) (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Quarterly financial data (unaudited) [Abstract]
Legal settlement charge associated with proposed settlement of allegations	$ (780)			$ (780)
Legal settlement charge associated with proposed settlement of allegations (net of tax)	(705)
Income tax benefit for resolving certain transfer pricing issues with tax authorities		113
Impairment of fixed assets (net of tax)		74
Impairment of fixed assets		118		6	118	21
Income tax benefit as the result of resolving certain transfer pricing issues with tax authorities for prior periods			$ 38