Borrowings (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended										3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Mar. 31, 2012 5.125% senior notes due 2020	Dec. 31, 2011 5.125% senior notes due 2020	Dec. 09, 2010 5.125% senior notes due 2020	Mar. 31, 2012 5.125% senior notes due 2020 Significant Observable Inputs (Level 2)	Mar. 31, 2012 6.125% senior notes due 2016	Dec. 31, 2011 6.125% senior notes due 2016	Mar. 31, 2012 6.125% senior notes due 2016 Significant Observable Inputs (Level 2)	Mar. 31, 2012 Revolving credit facility D	Dec. 31, 2011 Revolving credit facility	Mar. 31, 2012 Uncommitted line of credit	Dec. 31, 2011 Uncommitted line of credit	Mar. 31, 2012 Industrial development and revenue bonds through 2018	Dec. 31, 2011 Industrial development and revenue bonds through 2018	Mar. 31, 2012 Other, including capital lease obligations	Dec. 31, 2011 Other, including capital lease obligations
Borrowings
Total long-term debt	$ 766.4		$ 762.4	$ 249.0	$ 249.0			$ 149.5	$ 149.5		$ 360.0	$ 348.0			$ 5.5	$ 5.5	$ 2.4	$ 10.4
Less current portion	(162.1)		(158.1)								(160.0)
Total long-term debt, net of current portion	604.3		604.3								200.0
Interest rate (as a percent)				5.125%	5.125%	5.125%		6.125%	6.125%
Unamortized discount				1.0	1.0			0.5	0.5
Par value of senior notes				250				150
Fair value of notes							270.2			166.8
Maximum borrowing capacity											360.0		45.0	35.0
Remaining borrowing capacity											240.0
Amount borrowed and outstanding in connection with the financing of the acquisition											310.2
Short-term debt, including current maturities	162.1		158.1								160.0
Number of days from the funding within which amount is payable											30
Outstanding issued letters of credit	31.1
Cash payments for interest	5.9	4.7
Interest income	$ 0.1	$ 0.2
Average interest rate (as a percent)													1.50%	1.50%