Derivative Instruments and Hedging Activities - Gains and Losses (Details) - Not designated as hedging instruments - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative instruments and hedging activities
Impact on net income of unrealized gains and losses resulting from changes in fair value of derivative instruments	$ 1.1	$ (2.5)	$ (6.6)	$ 1.0
Foreign exchange contracts
Derivative instruments and hedging activities
Impact on net income of unrealized gains and losses resulting from changes in fair value of derivative instruments	1.4	(1.5)	(6.7)	5.5
Embedded derivatives in purchase and delivery contracts
Derivative instruments and hedging activities
Impact on net income of unrealized gains and losses resulting from changes in fair value of derivative instruments		(1.3)	1.3	(5.0)
Fixed price commodity contracts
Derivative instruments and hedging activities
Impact on net income of unrealized gains and losses resulting from changes in fair value of derivative instruments	$ (0.3)	$ 0.3	$ (1.2)	$ 0.5