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Nominal or face amount used to calculate payment on derivative.

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Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Net assets associated with foreign currency derivatives	$ (7.9)		$ (7.9)		$ (10.7)
Maturity period of derivatives (in months)			18 months
Estimated amount of net gains (losses) associated with derivative instruments, net of tax, in next twelve months			$ (5.0)
Designated as Hedging Instrument \| Foreign Exchange Forward \| Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	212.6		212.6
Designated as Hedging Instrument \| United Kingdom, Pounds \| Foreign Exchange Forward \| Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	116.7		116.7
Designated as Hedging Instrument \| Australia, Dollars \| Foreign Exchange Forward \| Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	44.6		44.6
Designated as Hedging Instrument \| Euro Member Countries, Euro \| Foreign Exchange Forward \| Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	18.2		18.2
Designated as Hedging Instrument \| Singapore, Dollars \| Foreign Exchange Forward \| Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	9.5		9.5
Designated as Hedging Instrument \| Norway, Krone \| Foreign Exchange Forward \| Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	16.5		16.5
Designated as Hedging Instrument \| Brazil, Brazil Real \| Foreign Exchange Forward \| Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	7.1		7.1
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) on derivatives not designated as hedging instruments	(2.3)	$ 2.2	(7.6)	$ 9.7
Not Designated as Hedging Instrument \| Foreign Exchange Forward \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	27.1		27.1
Not Designated as Hedging Instrument \| United Kingdom, Pounds \| Foreign Exchange Forward \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	7.8		7.8
Not Designated as Hedging Instrument \| Nigeria, Nairas \| Foreign Exchange Forward \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	9.6		9.6
Not Designated as Hedging Instrument \| Israel, New Shekels \| Foreign Exchange Forward \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	6.6		6.6
Not Designated as Hedging Instrument \| Mexico, Pesos \| Foreign Exchange Forward \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	$ 3.1		$ 3.1