Debt - Maturing within One Year (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Short-term foreign debt	$ 43.8	$ 91.4
Commercial paper	184.4	0.0
Total short-term debt	228.2	91.4
Current portion of long-term debt	100.7	101.2
Short-term debt and current portion of long-term debt	$ 328.9	$ 192.6
Short-term foreign debt
Short-term Debt [Line Items]
Average interest rate	7.90%
Commercial paper
Short-term Debt [Line Items]
Average interest rate	2.50%