Debt (Details) (USD $)			0 Months Ended	1 Months Ended		9 Months Ended					9 Months Ended					9 Months Ended					3 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Aug. 16, 2012 2011 Credit Agreement	Jun. 30, 2012 2011 Credit Agreement	Apr. 02, 2011 2011 Credit Agreement	Sep. 30, 2012 2011 term loan A	Dec. 31, 2011 2011 term loan A	Apr. 02, 2011 2011 term loan A	Sep. 30, 2012 2011 term loan A Minimum	Sep. 30, 2012 2011 term loan A Maximum	Sep. 30, 2012 2011 term loan B	Dec. 31, 2011 2011 term loan B	Apr. 02, 2011 2011 term loan B	Sep. 30, 2012 2011 term loan B Minimum	Sep. 30, 2012 2011 term loan B Maximum	Sep. 30, 2012 Revolving Credit Facility	Aug. 16, 2012 Revolving Credit Facility	Jan. 20, 2012 Revolving Credit Facility	Dec. 31, 2011 Revolving Credit Facility	Apr. 02, 2011 Revolving Credit Facility	Sep. 30, 2012 2011 Revolving Credit Facility and 2011 term loan A	Sep. 30, 2012 2011 Revolving Credit Facility and 2011 term loan A Minimum	Sep. 30, 2012 2011 Revolving Credit Facility and 2011 term loan A Maximum	Sep. 30, 2012 Other	Dec. 31, 2011 Other
Debt instrument
Total debt	$ 2,347,541,000	$ 2,325,715,000				$ 854,674,000	$ 894,837,000				$ 1,273,326,000	$ 1,333,163,000				$ 158,601,000			$ 10,000,000					$ 60,940,000	$ 87,715,000
Less current debt	(69,327,000)	(56,695,000)
Total long term debt	2,278,214,000	2,269,020,000
Weighted average stated interest rate (as a percent)						3.41%					4.00%					4.22%
Debt agreements
Principal amount of credit agreement								950,000,000					1,400,000,000
Maximum borrowing capacity					2,725,000,000															375,000,000
General investment basket available amount																	325,000,000
Payments of outstanding principal balances of the term loans				100,000,000
Increase in interest margin once the total leverage ratio of the Company is greater than 3.25:1			0.25%
Minimum leverage ratio requirement for increase in interest margin by 0.25%			3.25
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																49,600,000
Availability for future borrowings under the Revolver																166,800,000
Rate of LIBOR floor (as a percent)														1.00%
Basis spread on variable rate (as a percent)									2.25%	3.25%				2.75%	3.25%							2.25%	3.25%
Maximum revolver sublimit borrowing capacity in Canada																		$ 275,000,000		$ 150,000,000