Financial Instruments - Realized and Unrealized (Losses) Gains Associated with Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Foreign exchange and metals contracts | Other income, net | Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of loss recognized in income on derivatives	$ 12.9	$ (1.1)	$ 10.9	$ (2.5)