Long-Term Debt, Schedule of Debt (Details) - USD ($) $ in Millions	Dec. 31, 2017	Apr. 05, 2017	Dec. 31, 2016
Long-Term Debt
Less deferred debt issuance costs	$ (12.9)		$ (12.3)
Total debt	3,542.6		3,010.7
Less current portion	1.1		375.2
Total long-term debt	3,541.5		2,635.5
Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	3,588.4		3,062.2
Less short-term debt, Approximate Fair Value	1.1		375.7
Long-term debt, Approximate Fair Value	3,587.3		2,686.5
Commercial Paper Program
Long-Term Debt
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	1,175.4		1,018.9
Unamortized discount	0.3		0.4
Commercial Paper Program | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 1,175.4		1,018.9
4.00% Senior Notes due February 2022
Long-Term Debt
Stated interest rate (as a percent)	4.00%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 499.5		499.4
Unamortized discount	0.5		0.6
4.00% Senior Notes due February 2022 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 522.5		523.7
2.55% Senior Notes due January 2019
Long-Term Debt
Stated interest rate (as a percent)	2.55%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 749.8		749.5
Unamortized discount	0.2		0.5
2.55% Senior Notes due January 2019 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 752.8		$ 758.3
1.55% Senior Notes due September 2017
Long-Term Debt
Stated interest rate (as a percent)			1.55%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs			$ 374.9
Unamortized discount			0.1
1.55% Senior Notes due September 2017 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value			375.4
3.125% Senior Notes due September 2021
Long-Term Debt
Stated interest rate (as a percent)	3.125%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 374.8		374.8
Unamortized discount	0.2		0.2
3.125% Senior Notes due September 2021 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 381.2		380.4
2.20% Senior Notes due April 2020
Long-Term Debt
Stated interest rate (as a percent)	2.20%	2.20%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 399.8
Unamortized discount	0.2
2.20% Senior Notes due April 2020 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 398.0
3.20% Senior Notes due April 2024
Long-Term Debt
Stated interest rate (as a percent)	3.20%	3.20%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	$ 349.6
Unamortized discount	0.4
3.20% Senior Notes due April 2024 | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	351.9
Notes payable to foreign banks and other debt
Long-Term Debt
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	6.6		5.5
Notes payable to foreign banks and other debt | Quoted Prices in Active Markets for Identical Assets (Level 1)
Long-Term Debt
Total debt, Approximate Fair Value	$ 6.6		$ 5.5