Derivative Instruments (Notional Amounts) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	$ 296.5	$ 172.0
Not Designated as Hedging Instrument [Member]
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	$ 46.1	0.0
Maturities of cash flow hedge derivatives	1 month
Cash flow hedging [Member] | Cash flow hedges [Member]
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	$ 250.4	$ 172.0
Maturities of cash flow hedge derivatives	18 months