Derivative Instruments and Hedging Activities - Gains and Losses (Details) - Not designated as hedging instruments - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Derivative instruments and hedging activities
Impact on net income of unrealized gains and losses resulting from changes in fair value of derivative instruments	$ (6.8)	$ 0.7	$ 4.2
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	(7.0)	5.8	(0.1)
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	1.5	(5.7)	3.7
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	$ (1.3)	$ 0.6	$ 0.6