Financial Instruments - Additional Derivative Information (Details) - Foreign currency exchange contract [Member] - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Not designated as hedging instrument [Member]
Derivative [Line Items]
Derivative, notional amount	$ 93.6	$ 177.0
Cash flow hedges [Member] | Designated as hedging instrument [Member]
Derivative [Line Items]
Derivative, notional amount based on forecasted revenue	142.7	20.0
Derivative, notional amount based on forecasted expense	$ 0.0	$ 20.9