Debt - Long-term (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total long-term debt	$ 3,113.9	$ 2,531.0
Debt issuance cost	(20.2)	(8.9)
Less: debt maturing within one year	82.8	386.0
Total long-term debt, less current portion	3,031.1	2,145.0
Pollution Control and Industrial Revenue Bonds
Debt Instrument [Line Items]
Unamortized discount	0.2	0.2
Total long-term debt	51.6	51.6
Senior Notes
Debt Instrument [Line Items]
Unamortized discount	1.3	0.8
Total long-term debt	$ 2,198.7	999.2
2017 Term Loan Facility
Debt Instrument [Line Items]
Interest rate percentage	3.00%
Long-term debt, gross	$ 800.0	1,400.0
Revolving Credit Facility
Debt Instrument [Line Items]
Interest rate percentage	4.30%
Long-term debt, gross	$ 0.0	0.0
Letters of credit outstanding, amount	217.0
Line of credit, remaining borrowing capacity	1,283.0
Foreign debt
Debt Instrument [Line Items]
Total long-term debt	$ 83.8	$ 89.1
Minimum \| Pollution Control and Industrial Revenue Bonds
Debt Instrument [Line Items]
Interest rate percentage	1.85%
Minimum \| Senior Notes
Debt Instrument [Line Items]
Interest rate percentage	3.20%
Minimum \| Foreign debt
Debt Instrument [Line Items]
Interest rate percentage	0.00%
Maximum \| Pollution Control and Industrial Revenue Bonds
Debt Instrument [Line Items]
Interest rate percentage	6.45%
Maximum \| Senior Notes
Debt Instrument [Line Items]
Interest rate percentage	4.50%
Maximum \| Foreign debt
Debt Instrument [Line Items]
Interest rate percentage	7.20%

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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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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