Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Weighted average interest rate	0.40%
Long-term Debt	$ 1,417.9	$ 1,568.2
Commercial paper, maximum amount outstanding during period	399.0
Commercial paper, average outstanding amount	235.7
Line of credit, maximum borrowing capacity	800
Line of Credit Facility, Maximum Borrowing Capacity, Multicurrency Limit	100
Derivative Instruments, Gain (Loss) Recognized in Income, Net	7.8	0.3	(4.6)
Current portion of long-term debt	0.3	13.4
Long-term Debt and Capital Lease Obligations	1,417.6	1,554.8
Long-term Debt, Fiscal Year Maturity [Abstract]
2013	203.8
2014	399.8
2015	0
2016	0
2017	0
Commercial Paper [Member]
Debt Instrument [Line Items]
Weighted average interest rate	0.40%
Long-term Debt	203.8	46.5
Notes Payable 4.875 Percent Due April 1 2012 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	4.875%
Long-term Debt	0	300.0
Proceeds from (Repayments of) Debt	300
Industrial Revenue Bond Payable 1.6 Percent Due 2012 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	1.60%
Long-term Debt	0	8.0
Notes Payable 5.65 Percent Due 2014 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	5.65%
Long-term Debt	399.8	399.7
Unamortized discount	0.2	0.3
Notes Payable 6.8 Percent Due 2019 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	6.80%
Long-term Debt	399.2	399.1
Unamortized discount	0.8	0.9
Notes Payable 4.5 Percent Due 2021 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	4.50%
Long-term Debt	414.7	400.7
Debt instrument, face amount	400
Fixed-rate (as a percent)		4.50%
Unamortized discount	2.3	2.5
Debt of Subsidiary Companies Due 2013 [Member]
Debt Instrument [Line Items]
Long-term Debt	0	13.6
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term Debt	0.4	0.6
Interest-rate swap | Measured on a recurring basis | (Level 2)
Debt Instrument [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	17.0	3.3
Derivatives designated as hedging instruments | Interest-rate swap
Debt Instrument [Line Items]
Number of swap agreements		4
Notional amounts of derivatives		400.0
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 7.0	$ 1.6	$ 0