Financing arrangements (Details Textual) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended									12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended			12 Months Ended		12 Months Ended			12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended			12 Months Ended			12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended							12 Months Ended				12 Months Ended	1 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Feb. 28, 2011 0.125% convertible notes due 2011 (0.125% 2011 Convertible Notes) [Member] USD ($)	Dec. 31, 2011 0.125% convertible notes due 2011 (0.125% 2011 Convertible Notes) [Member] USD ($)	Dec. 31, 2010 0.125% convertible notes due 2011 (0.125% 2011 Convertible Notes) [Member] USD ($)	Dec. 31, 2012 0.375% convertible notes due 2013 (0.375% 2013 Convertible Notes) [Member] USD ($)	Dec. 31, 2011 0.375% convertible notes due 2013 (0.375% 2013 Convertible Notes) [Member] USD ($)	Dec. 31, 2010 0.375% convertible notes due 2013 (0.375% 2013 Convertible Notes) [Member] USD ($)	Dec. 31, 2012 1.875% notes due 2014 (1.875% 2014 Notes) [Member] USD ($)	Dec. 31, 2011 1.875% notes due 2014 (1.875% 2014 Notes) [Member] USD ($)	Dec. 31, 2012 4.85% notes due 2014 (4.85% 2014 Notes) [Member] USD ($)	Dec. 31, 2011 4.85% notes due 2014 (4.85% 2014 Notes) [Member] USD ($)	Dec. 31, 2012 2.30% notes due 2016 (2.30% 2016 Notes) [Member] USD ($)	Dec. 31, 2011 2.30% notes due 2016 (2.30% 2016 Notes) [Member] USD ($)	Dec. 31, 2012 2.50% notes due 2016 (2.50% 2016 Notes) [Member] USD ($)	Dec. 31, 2011 2.50% notes due 2016 (2.50% 2016 Notes) [Member] USD ($)	Dec. 31, 2012 2.125% notes due 2017 (2.125% 2017 Notes) [Member] USD ($)	Dec. 31, 2011 2.125% notes due 2017 (2.125% 2017 Notes) [Member] USD ($)	Dec. 31, 2012 5.85% notes due 2017 (5.85% 2017 Notes) [Member] USD ($)	Dec. 31, 2011 5.85% notes due 2017 (5.85% 2017 Notes) [Member] USD ($)	Dec. 31, 2012 6.15% notes due 2018 (6.15% 2018 Notes) [Member] USD ($)	Dec. 31, 2011 6.15% notes due 2018 (6.15% 2018 Notes) [Member] USD ($)	Dec. 31, 2012 4.375% euro denominated notes due 2018 (4.375% 2018 euro Notes) [Member] USD ($)	Dec. 31, 2011 4.375% euro denominated notes due 2018 (4.375% 2018 euro Notes) [Member] USD ($)	Dec. 31, 2011 4.375% euro denominated notes due 2018 (4.375% 2018 euro Notes) [Member] EUR (€)	Dec. 31, 2012 5.70% notes due 2019 (5.70% 2019 Notes) [Member] USD ($)	Dec. 31, 2011 5.70% notes due 2019 (5.70% 2019 Notes) [Member] USD ($)	Dec. 31, 2012 2.125% euro denominated notes due 2019 (2.125% 2019 euro Notes) [Member] USD ($)	Dec. 31, 2012 2.125% euro denominated notes due 2019 (2.125% 2019 euro Notes) [Member] EUR (€)	Dec. 31, 2011 2.125% euro denominated notes due 2019 (2.125% 2019 euro Notes) [Member] USD ($)	Dec. 31, 2012 4.50% notes due 2020 (4.50% 2020 Notes) [Member] USD ($)	Dec. 31, 2011 4.50% notes due 2020 (4.50% 2020 Notes) [Member] USD ($)	Dec. 31, 2012 3.45% notes due 2020 (3.45% 2020 Notes) [Member] USD ($)	Dec. 31, 2011 3.45% notes due 2020 (3.45% 2020 Notes) [Member] USD ($)	Dec. 31, 2012 4.10% notes due 2021 (4.10% 2021 Notes) [Member] USD ($)	Dec. 31, 2011 4.10% notes due 2021 (4.10% 2021 Notes) [Member] USD ($)	Dec. 31, 2012 3.875% notes due 2021 (3.875% 2021 Notes) [Member] USD ($)	Dec. 31, 2011 3.875% notes due 2021 (3.875% 2021 Notes) [Member] USD ($)	Dec. 31, 2012 3.625% notes due 2022 (3.625% 2022 Notes) [Member] USD ($)	Dec. 31, 2011 3.625% notes due 2022 (3.625% 2022 Notes) [Member] USD ($)	Dec. 31, 2012 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member] USD ($)	Dec. 31, 2011 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member] USD ($)	Dec. 31, 2011 5.50% pound sterling denominated notes due 2026 (5.50% 2026 pound sterling Notes) [Member] GBP (£)	Dec. 31, 2012 4.00% pound sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member] USD ($)	Dec. 31, 2012 4.00% pound sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member] GBP (£)	Dec. 31, 2011 4.00% pound sterling denominated notes due 2029 (4.00% 2029 pound sterling Notes) [Member] USD ($)	Dec. 31, 2012 6.375% notes due 2037 (6.375% 2037 Notes) [Member] USD ($)	Dec. 31, 2011 6.375% notes due 2037 (6.375% 2037 Notes) [Member] USD ($)	Dec. 31, 2012 6.90% notes due 2038 (6.90% 2038 Notes) [Member] USD ($)	Dec. 31, 2011 6.90% notes due 2038 (6.90% 2038 Notes) [Member] USD ($)	Dec. 31, 2012 6.40% notes due 2039 (6.40% 2039 Notes) [Member] USD ($)	Dec. 31, 2011 6.40% notes due 2039 (6.40% 2039 Notes) [Member] USD ($)	Dec. 31, 2012 5.75% notes due 2040 (5.75% 2040 Notes) [Member] USD ($)	Dec. 31, 2011 5.75% notes due 2040 (5.75% 2040 Notes) [Member] USD ($)	Dec. 31, 2012 4.95% notes due 2041 (4.95% 2041 Notes) [Member] USD ($)	Dec. 31, 2011 4.95% notes due 2041 (4.95% 2041 Notes) [Member] USD ($)	Dec. 31, 2012 5.15% notes due 2041 (5.15% 2041 Notes) [Member] USD ($)	Dec. 31, 2011 5.15% notes due 2041 (5.15% 2041 Notes) [Member] USD ($)	Dec. 31, 2012 5.65% notes due 2042 (5.65% 2042 Notes) [Member] USD ($)	Dec. 31, 2011 5.65% notes due 2042 (5.65% 2042 Notes) [Member] USD ($)	Dec. 31, 2012 5.375% notes due 2043 (5.375% 2043 Notes) [Member] USD ($)	Dec. 31, 2011 5.375% notes due 2043 (5.375% 2043 Notes) [Member] USD ($)	Dec. 31, 2012 Warrants Issued Concurrent with Issuance of 2011 and 2013 Convertible Debt [Member]	Dec. 31, 2006 Convertible notes [Member] USD ($)	Dec. 31, 2011 Zero coupon convertible notes due in 2032 [Member] USD ($)	Dec. 31, 2012 8.125% notes due 2097 (Other) [Member] USD ($)	Dec. 31, 2011 8.125% notes due 2097 (Other) [Member] USD ($)	Dec. 31, 2012 Commercial Paper [Member] USD ($)	Dec. 31, 2011 Commercial Paper [Member] USD ($)	Dec. 31, 2012 Line of Credit [Member] USD ($) extension	Dec. 31, 2011 Line of Credit [Member] USD ($)	Dec. 31, 2011 Rate Adjustment To Libor On Interest Rate Swap Agreements [Member]	Dec. 31, 2010 Rate Adjustment To Libor On Interest Rate Swap Agreements [Member]	Dec. 31, 2012 Interest Rate Swap [Member] USD ($)	Feb. 27, 2013 Subsequent Event [Member] 0.375% convertible notes due 2013 (0.375% 2013 Convertible Notes) [Member] USD ($)	Feb. 27, 2013 Subsequent Event [Member] Repayment of Debt [Member] 0.375% convertible notes due 2013 (0.375% 2013 Convertible Notes) [Member] USD ($)	Feb. 27, 2013 Excess Conversion Value [Member] Subsequent Event [Member] 0.375% convertible notes due 2013 (0.375% 2013 Convertible Notes) [Member] USD ($)	Dec. 31, 2012 MN [Member] USD ($)	Dec. 31, 2012 Shelf Registration Statement [Member] Medium-term Notes [Member] USD ($)	Dec. 31, 2011 Shelf Registration Statement [Member] Medium-term Notes [Member] USD ($)
Financing arrangements (Textual) [Abstract]
Repayment of debt	$ 123,000,000	$ 2,500,000,000	$ 0
Stated contractual interest rate on note						0.125%	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%	4.375%	5.70%	5.70%	2.125%	2.125%		4.50%	4.50%	3.45%	3.45%	4.10%	4.10%	3.875%	3.875%	3.625%		5.50%	5.50%	5.50%	4.00%	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%
Repayments of convertible notes				2,500,000,000																																																																								2,500,000,000		99,000,000
Aggregate principal amount of notes issued	5,000,000,000	10,500,000,000	2,500,000,000				2,500,000,000																			550,000,000				675,000,000														475,000,000		700,000,000																			5,000,000,000
Total debt issuance costs	25,000,000	55,000,000	17,000,000
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%		101.00%		101.00%			101.00%		101.00%	101.00%		101.00%		101.00%		101.00%		101.00%		101.00%		101.00%			101.00%	101.00%		101.00%		101.00%		101.00%		101.00%		101.00%		101.00%		101.00%		101.00%
Convertible notes conversion ratio into common stock							12.8809
Principal amount of notes to which the common stock conversion ratio is applied							1,000
Conversion price per share of convertible notes							$ 77.63
Ratio of closing price of common stock to respective conversion price per share that needs to be exceeded in previous quarter to allow conversion							130.00%
Conversion of convertible notes before maturity period							within one month
Cash settlement of convertible bond hedge																																																																													99,000,000
Potential settlements of warrants (In May 2013) (in shares)																																																																31.5
Exercise price of warrants																																																																105.48
Warrants to acquire shares of our common stock , expired (in shares)																																																																31.3
Effective interest rate on convertible notes					6.24%	6.24%	6.35%	6.35%	6.35%
Interest expense, net	1,053,000,000	610,000,000	604,000,000		13,000,000	149,000,000	151,000,000	143,000,000	134,000,000
Non-cash interest expense					12,000,000	146,000,000	142,000,000	133,000,000	125,000,000
Total noncurrent debt	24,034,000,000	21,344,000,000								1,000,000,000	1,000,000,000	1,000,000,000	1,000,000,000	749,000,000	748,000,000	999,000,000	999,000,000	1,248,000,000		1,099,000,000	1,099,000,000	499,000,000	499,000,000	723,000,000	714,000,000		999,000,000	998,000,000	887,000,000			300,000,000	300,000,000	897,000,000	897,000,000	998,000,000	998,000,000	1,745,000,000	1,745,000,000	747,000,000		763,000,000	739,000,000		1,117,000,000			899,000,000	899,000,000	499,000,000	499,000,000	996,000,000	996,000,000	697,000,000	697,000,000	595,000,000	595,000,000	2,232,000,000	2,232,000,000	1,244,000,000	1,244,000,000	1,000,000,000					100,000,000	100,000,000											9,000,000
Other convertible notes, current							2,488,000,000																																																											84,000,000
Interest rate swap contracts - fair value hedge - notional amounts		3,600,000,000	3,600,000,000
Derivative lower range variable interest rate																																																																									0.30%	0.30%
Derivative higher range variable interest rate																																																																									2.60%	2.60%
Maximum borrowing capacity under commercial paper program																																																																					2,500,000,000
Amount outstanding under commercial paper program																																																																					0	0
Maximum current borrowing capacity under a syndicated, unsecured, revolving credit agreement																																																																							2,500,000,000
Amount by which the borrowing capacity under a syndicated, unsecured, revolving credit agreement maybe increased upon our request at the discretion of the banks																																																																							500,000,000
Initial commitment term of each bank which is a party to the agreement																																																																							5 years
Number of additional extensions																																																																							2
Additional period for extension of commitment term																																																																							1 year
Annual commitment fees for syndicated, unsecured, revolving credit agreement																																																																							0.10%
Interest rate charged over LIBOR on any amounts borrowed under the facility																																																																							0.90%
Amount outstanding under syndicated, unsecured, revolving credit facility																																																																							0	0
Previous revolving credit facilities, terminated in period																																																																							2,300,000,000
Amount that may be issued under a medium term note program established under the shelf registration statement																																																																																400,000,000
Amount outstanding under medium term note program																																																																																0	0
Interest costs capitalized	26,000,000	22,000,000	33,000,000
Interest paid, net of interest rate swaps	406,000,000	446,000,000	323,000,000
Receipt from counterparties upon termination of interest rate swap contracts																																																																											$ 397,000,000