Income taxes (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income taxes (Textual) [Abstract]
Increase (decrease) in valuation allowance for deferred tax assets	$ 46,000,000	$ (12,000,000)
Interest and penalties related to unrecognized tax benefits recognized in income tax provision	23,000,000	41,000,000	57,000,000
Accrued interest and penalties associated with unrecognized tax benefits	105,000,000	90,000,000
Total foreign income before income taxes	2,600,000,000	3,100,000,000	3,100,000,000
Income taxes paid	595,000,000	1,344,000,000	497,000,000
Decrease in unrecognized tax benefits that is reasonably possible within the succeeding twelve months due to potential tax settlements	270,000,000
Investments in Foreign Subsidiaries and Foreign Corporate Joint Ventures that are Essentially Permanent in Duration [Member]
Deferred Tax Liability Not Recognized [Line Items]
Undistributed earnings of our foreign operations that are intended to be invested indefinitely outside of the United States	19,500,000,000
Additional income taxes required to be accrued and paid if earnings of foreign operations that are intended to be indefinitely invested outside of the United States were repatriated	6,900,000,000
State taxing jurisdictions' [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforwards available to reduce income taxes	176,000,000
Tax credit carryforwards for which a full valuation allowance has been provided	67,000,000
Domestic Country [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforwards available to reduce income taxes	44,000,000
Tax credit carryforwards for which a full valuation allowance has been provided	$ 44,000,000
Puerto Rico Excise Tax [Member]
Excise Tax Rate [Line Items]
Period of excise tax imposed	6 years
Effective excise tax rate for 2011	4.00%
Effective excise tax rate for 2012	3.75%
Effective excise tax rate for 2013	2.75%
Effective excise tax rate for 2014	2.50%
Effective excise tax rate for 2015	2.25%
Effective excise tax rate for 2016	1.00%