Debt (Details) (USD $)	9 Months Ended			1 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Aug. 31, 2012 5.375% Senior Notes Due August 2012	Sep. 30, 2012 5.375% Senior Notes Due August 2012	Dec. 31, 2011 5.375% Senior Notes Due August 2012	Sep. 30, 2012 6.15% Senior Notes Due February 2018	Dec. 31, 2011 6.15% Senior Notes Due February 2018	Sep. 30, 2012 9.25% Senior Notes Due January 2019	Dec. 31, 2011 9.25% Senior Notes Due January 2019	Sep. 30, 2012 5.00% senior notes due September 2020	Dec. 31, 2011 5.00% senior notes due September 2020	Sep. 30, 2012 4.625% senior notes due September 2021	Dec. 31, 2011 4.625% senior notes due September 2021	Sep. 30, 2012 Revolving Credit Facility	Dec. 31, 2011 Revolving Credit Facility
Long-term debt
Senior Notes						$ 274,604,000	$ 968,403,000	$ 967,490,000	$ 1,125,000,000	$ 1,125,000,000	$ 697,572,000	$ 697,343,000	$ 697,847,000	$ 697,667,000
Revolving credit facilities															1,190,000,000	860,000,000
Other	463,000		1,712,000
Long-term Debt	4,679,285,000		4,623,816,000
Current portion of long-term debt	389,000		275,326,000
Long-term debt, Noncurrent	4,678,896,000		4,348,490,000
Interest rate on senior note due (as a percent)					5.375%		6.15%		9.25%		5.00%		4.625%
Payment of debt	276,232,000	1,404,271,000		282,400,000
Payment of debt principal				275,000,000
Payment of debt accrued interest				7,400,000
Payment of debt, portion financed through line of credit borrowings				$ 270,000,000