Debt - Long-term (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt issuance cost	$ (17.8)	$ (19.8)
Total long-term debt	3,018.3	3,023.1
Less: debt maturing within one year	386.6	93.6
Total long-term debt, less current portion	$ 2,631.7	2,929.5
Revolving Credit Facility \| Line of Credit
Debt Instrument [Line Items]
Interest Rate Percentage	2.78%
Long-term debt, gross	$ 0.0	0.0
Letters of credit outstanding amount	238.1
Pollution Control and Industrial Revenue Bonds
Debt Instrument [Line Items]
Unamortized discount	0.1	0.1
Long-term debt, gross	$ 49.9	51.6
Pollution Control and Industrial Revenue Bonds \| Minimum
Debt Instrument [Line Items]
Interest Rate Percentage	6.45%
Senior Notes
Debt Instrument [Line Items]
Unamortized discount	$ 0.8	1.0
Long-term debt, gross	$ 2,199.2	2,199.0
Senior Notes \| Minimum
Debt Instrument [Line Items]
Interest Rate Percentage	3.20%
Senior Notes \| Maximum
Debt Instrument [Line Items]
Interest Rate Percentage	4.50%
2017 Term Loan Facility
Debt Instrument [Line Items]
Interest Rate Percentage	1.33%
Long-term debt, gross	$ 700.0	700.0
Revolving Credit Facility
Debt Instrument [Line Items]
Credit agreement, available funds	994.3
Foreign debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 87.0	$ 92.3
Foreign debt \| Minimum
Debt Instrument [Line Items]
Interest Rate Percentage	0.00%
Foreign debt \| Maximum
Debt Instrument [Line Items]
Interest Rate Percentage	7.10%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after accumulated amortization, of debt discount.

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Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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