Long-Term Debt and Capital Leases and Letters of Credit - Long-Term Debt (Details)	Sep. 30, 2018 EUR (€)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Total debt		$ 834,500,000	$ 1,068,200,000
Less: current portion of long-term debt and debt issuance costs		(14,700,000)	(4,300,000)
Total long-term debt		819,800,000	1,063,900,000
Other debt at various rates due through 2018
Debt Instrument [Line Items]
Total debt		5,300,000	2,700,000
Credit facility \| $750.0 million credit facility due December 2020, weighted average rate of 2.72% at December 31, 2017
Debt Instrument [Line Items]
Total debt		0	$ 165,000,000
Weighted average interest rate			2.72%
Line of credit facility, current borrowing capacity			$ 750,000,000
Term Loans \| Term loans due through January 2022, weighted average rate of 3.37% at September 30, 2018 and 2.94% at December 31, 2017
Debt Instrument [Line Items]
Total debt		$ 114,000,000	$ 175,500,000
Weighted average interest rate	3.37%	3.37%	2.94%
Term Loans \| Term loan due October 2019, variable rate of 3.36% swapped to a Euro fixed rate of 0.7055%
Debt Instrument [Line Items]
Total debt		$ 100,000,000	$ 100,000,000
Stated interest rate	0.7055%	0.7055%
Effective interest rate	3.36%	3.36%
Senior Notes \| 2.61% Fixed Rate Senior Notes due December 2019
Debt Instrument [Line Items]
Total debt		$ 30,000,000	30,000,000
Stated interest rate	2.61%	2.61%
Senior Notes \| 5.30% Fixed Rate Senior Notes due September 2020
Debt Instrument [Line Items]
Total debt		$ 75,000,000	75,000,000
Stated interest rate	5.30%	5.30%
Senior Notes \| 2.81% Fixed Rate Senior Notes due November 2020
Debt Instrument [Line Items]
Total debt		$ 25,000,000	25,000,000
Stated interest rate	2.81%	2.81%
Senior Notes \| 3.09% Fixed Rate Senior Notes due December 2021
Debt Instrument [Line Items]
Total debt		$ 95,000,000	95,000,000
Stated interest rate	3.09%	3.09%
Senior Notes \| 3.28% Fixed Rate Senior Notes due November 2022
Debt Instrument [Line Items]
Total debt		$ 100,000,000	100,000,000
Stated interest rate	3.28%	3.28%
Senior Notes \| 0.70% €50 Million Fixed Rate Senior Notes due April 2022
Debt Instrument [Line Items]
Total debt		$ 58,000,000	60,000,000
Stated interest rate	0.70%	0.70%
Debt instrument, face amount (in eur) \| €	€ 50,000,000
Senior Notes \| 0.92% €100 Million Fixed Rate Senior Notes due April 2023
Debt Instrument [Line Items]
Total debt		$ 116,100,000	120,000,000
Stated interest rate	0.92%	0.92%
Debt instrument, face amount (in eur) \| €	€ 100,000,000
Senior Notes \| 1.09% €100 Million Fixed Rate Senior Notes due April 2024
Debt Instrument [Line Items]
Total debt		$ 116,100,000	$ 120,000,000
Stated interest rate	1.09%	1.09%
Debt instrument, face amount (in eur) \| €	€ 100,000,000

Long Term Debt, Current Maturities and Debt Issuance Costs, Net

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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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