Summary of Short-Term Borrowings and Long-Term Debt (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Short-term borrowings
Commercial paper issuances	$ 0	$ 268,700,000
Various debt due to international banks	1,800,000	2,200,000
Total short-term borrowings	1,800,000	270,900,000
Long-term debt
Debt issuance costs, net	(13,100,000)	(15,500,000)
Fair value adjustment asset (liability) related to hedged fixed rate debt instrument	(3,000,000)	(2,200,000)
Total long-term debt	2,105,300,000	2,103,400,000
Less: current maturities	(596,500,000)	0
Net long-term debt	1,508,800,000	2,103,400,000
Floating Rate Senior notes due January 25, 2019
Long-term debt
Senior notes	300,000,000	300,000,000
2.45% Senior notes due December 15, 2019
Long-term debt
Senior notes	300,000,000	300,000,000
Less: Discount	0	(100,000)
2.45% Senior notes due August 1, 2022
Long-term debt
Senior notes	300,000,000	300,000,000
Less: Discount	(300,000)	(300,000)
2.875% Senior notes due October 1, 2022
Long-term debt
Senior notes	400,000,000	400,000,000
Less: Discount	(100,000)	(200,000)
3.15% Senior notes due August 1, 2027
Long-term debt
Senior notes	425,000,000	425,000,000
Less: Discount	(400,000)	(400,000)
3.95% Senior notes due August 1, 2047
Long-term debt
Senior notes	400,000,000	400,000,000
Less: Discount	$ (2,800,000)	$ (2,900,000)