Financing arrangements (Details Textual) In Millions, unless otherwise specified	9 Months Ended													9 Months Ended							9 Months Ended											9 Months Ended			9 Months Ended															9 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	May 31, 2012 USD ($)	Sep. 30, 2012 0.375% convertible notes due 2013 (0.375% 2013 Convertible Notes) [Member]	Dec. 31, 2011 0.375% convertible notes due 2013 (0.375% 2013 Convertible Notes) [Member]	Sep. 30, 2012 1.875% notes due 2014 (1.875% 2014 Notes) [Member]	Dec. 31, 2011 1.875% notes due 2014 (1.875% 2014 Notes) [Member]	Sep. 30, 2012 4.85% notes due 2014 (4.85% 2014 Notes) [Member]	Dec. 31, 2011 4.85% notes due 2014 (4.85% 2014 Notes) [Member]	Sep. 30, 2012 2.30% notes due 2016 (2.30% 2016 Notes) [Member]	Dec. 31, 2011 2.30% notes due 2016 (2.30% 2016 Notes) [Member]	Sep. 30, 2012 2.50% notes due 2016 (2.50% 2016 Notes) [Member]	Dec. 31, 2011 2.50% notes due 2016 (2.50% 2016 Notes) [Member]	Sep. 30, 2012 2.125% notes due 2017 (2.125% 2017 Notes) [Member]	Sep. 30, 2012 5.85% notes due 2017 (5.85% 2017 Notes) [Member]	Dec. 31, 2011 5.85% notes due 2017 (5.85% 2017 Notes) [Member]	Sep. 30, 2012 6.15% notes due 2018 (6.15% 2018 Notes) [Member]	Dec. 31, 2011 6.15% notes due 2018 (6.15% 2018 Notes) [Member]	Sep. 30, 2012 4.375% euro denominated notes due 2018 (4.375% 2018 euro Notes) [Member]	Dec. 31, 2011 4.375% euro denominated notes due 2018 (4.375% 2018 euro Notes) [Member]	Sep. 30, 2012 2.125% euro denominated notes due 2019 (2.125% 2019 euro Notes) [Member] EUR (€)	Sep. 30, 2012 5.70% notes due 2019 (5.70% 2019 Notes) [Member]	Dec. 31, 2011 5.70% notes due 2019 (5.70% 2019 Notes) [Member]	Sep. 30, 2012 4.50% notes due 2020 (4.50% 2020 Notes) [Member]	Dec. 31, 2011 4.50% notes due 2020 (4.50% 2020 Notes) [Member]	Sep. 30, 2012 3.45% notes due 2020 (3.45% 2020 Notes) [Member]	Dec. 31, 2011 3.45% notes due 2020 (3.45% 2020 Notes) [Member]	Sep. 30, 2012 4.10% notes due 2021 (4.10% 2021 Notes) [Member]	Dec. 31, 2011 4.10% notes due 2021 (4.10% 2021 Notes) [Member]	Sep. 30, 2012 3.875% notes due 2021 (3.875% 2021 Notes) [Member]	Dec. 31, 2011 3.875% notes due 2021 (3.875% 2021 Notes) [Member]	Sep. 30, 2012 3.625% notes due 2022 (3.625% 2022 Notes) [Member]	Sep. 30, 2012 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member]	Dec. 31, 2011 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member]	Sep. 30, 2012 4.00% pound sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member] GBP (£)	Sep. 30, 2012 6.375% notes due 2037 (6.375% 2037 Notes) [Member]	Dec. 31, 2011 6.375% notes due 2037 (6.375% 2037 Notes) [Member]	Sep. 30, 2012 6.90% notes due 2038 (6.90% 2038 Notes) [Member]	Dec. 31, 2011 6.90% notes due 2038 (6.90% 2038 Notes) [Member]	Sep. 30, 2012 6.40% notes due 2039 (6.40% 2039 Notes) [Member]	Dec. 31, 2011 6.40% notes due 2039 (6.40% 2039 Notes) [Member]	Sep. 30, 2012 5.75% notes due 2040 (5.75% 2040 Notes) [Member]	Dec. 31, 2011 5.75% notes due 2040 (5.75% 2040 Notes) [Member]	Sep. 30, 2012 4.95% notes due 2041 (4.95% 2041 Notes) [Member]	Dec. 31, 2011 4.95% notes due 2041 (4.95% 2041 Notes) [Member]	Sep. 30, 2012 5.15% notes due 2041 (5.15% 2041 Notes) [Member]	Dec. 31, 2011 5.15% notes due 2041 (5.15% 2041 Notes) [Member]	Sep. 30, 2012 5.65% notes due 2042 (5.65% 2042 Notes) [Member]	Dec. 31, 2011 5.65% notes due 2042 (5.65% 2042 Notes) [Member]	Sep. 30, 2012 5.375% notes due 2043 (5.375% 2043 Notes) [Member]
Debt Instruments [Line Items]
Aggregate principal amount of notes issued	$ 2,000		$ 3,000																		€ 675														£ 700
Stated contractual interest rate on note				0.375%	0.375%	1.875%	1.875%	4.85%	4.85%	2.30%	2.30%	2.50%	2.50%	2.125%	5.85%	5.85%	6.15%	6.15%	4.375%	4.375%	2.125%	5.70%	5.70%	4.50%	4.50%	3.45%	3.45%	4.10%	4.10%	3.875%	3.875%	3.625%	5.50%	5.50%	4.00%	6.375%	6.375%	6.90%	6.90%	6.40%	6.40%	5.75%	5.75%	4.95%	4.95%	5.15%	5.15%	5.65%	5.65%	5.375%
Redemption price as a percentage of the principal amount of notes that may be required to be paid in the event of a change in control triggering event														101.00%							101.00%											101.00%			101.00%															101.00%
Financing arrangements (Textual) [Abstract]
Repayment of debt	102	2,500
Total debt issuance costs	$ 25