Financing arrangements (Details Textual 1) Share data in Millions, unless otherwise specified	12 Months Ended							12 Months Ended
	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2011 Cross Currency Swap [Member] USD ($)	Dec. 31, 2011 Cross Currency Swap [Member] GBP (£)	Dec. 31, 2011 Commercial Paper [Member] USD ($)	Dec. 31, 2010 Commercial Paper [Member] USD ($)	Dec. 31, 2011 Line of Credit [Member] USD ($)	Dec. 31, 2011 Medium-term Notes [Member] Self Registration Statement [Member] USD ($)	Dec. 31, 2010 Medium-term Notes [Member] Self Registration Statement [Member] USD ($)
Financing arrangements additional (Textual) [Abstract]
Interest paid, net of interest rate swaps	$ 446,000,000	$ 323,000,000	$ 293,000,000
Interest costs capitalized	22,000,000	33,000,000	32,000,000
Notional amount				748,000,000	475,000,000
Effective rate at which interest payments are received in Pounds Sterling under the cross currency swap contract				5.50%	5.50%
Warrants to acquire shares of our common stock , expired	31.3
Total debt issuance costs	55,000,000	17,000,000	13,000,000
Effective rate at which interest payments are made in US dollars under the cross currency swap contract				5.80%	5.80%
Amount that may be issued under a medium term note program established under the shelf registration statement									400,000,000
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
Interest rate charged over LIBOR on any amounts borrowed under the facility								0.90%
Annual commitment fees for syndicated, unsecured, revolving credit agreement								0.10%
Amount outstanding under commercial paper program						0	0
Previous revolving credit facilities, terminated in period								2,300,000,000
Amount outstanding under syndicated, unsecured, revolving credit facility								0
Amount outstanding under medium term note program									0	0
Maximum current borrowing capacity under a syndicated, unsecured, revolving credit agreement								2,500,000,000
Maximum borrowing capacity under commercial paper program						$ 2,500,000,000