Debt (Details) (USD $)			1 Months Ended		6 Months Ended					6 Months Ended					3 Months Ended	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 2011 Credit Agreement	Apr. 02, 2011 2011 Credit Agreement	Jun. 30, 2012 2011 term loan A	Dec. 31, 2011 2011 term loan A	Apr. 02, 2011 2011 term loan A	Jun. 30, 2012 2011 term loan A Minimum	Jun. 30, 2012 2011 term loan A Maximum	Jun. 30, 2012 2011 term loan B	Dec. 31, 2011 2011 term loan B	Apr. 02, 2011 2011 term loan B	Jun. 30, 2012 2011 term loan B Minimum	Jun. 30, 2012 2011 term loan B Maximum	Jun. 30, 2012 Revolving Credit Facility	Jun. 30, 2012 Revolving Credit Facility	Dec. 31, 2011 Revolving Credit Facility	Apr. 02, 2011 Revolving Credit Facility	Jun. 30, 2012 Revolving Credit Facility Minimum	Jun. 30, 2012 Revolving Credit Facility Maximum	Jun. 30, 2012 Other	Dec. 31, 2011 Other
Debt instrument
Total debt	$ 2,256,756,000	$ 2,325,715,000			$ 854,674,000	$ 894,837,000				$ 1,273,326,000	$ 1,333,163,000				$ 59,009,000	$ 59,009,000	$ 10,000,000				$ 69,747,000	$ 87,715,000
Less current debt	(49,890,000)	(56,695,000)
Total long term debt	2,206,866,000	2,269,020,000
Weighted average stated interest rate (as a percent)					3.46%					4.00%					4.22%	4.22%
Debt agreements
Principal amount of credit agreement							950,000,000					1,400,000,000
Revolving credit facility, maximum borrowing capacity				2,725,000,000														375,000,000
Payments of outstanding principal balances of the term loans			100,000,000
Debt instrument, description of variable rate basis					LIBOR or CDOR					LIBOR or CDOR					LIBOR or CDOR
Commitment fee on the unused portion (as a percent)																0.50%
Outstanding standby letters of credit															48,800,000	48,800,000
Availability for future borrowings under the Revolver															$ 267,200,000	$ 267,200,000
Rate of LIBOR floor (as a percent)													1.00%
Basis spread on variable rate (as a percent)								2.25%	3.00%				2.75%	3.00%					2.25%	3.00%