Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Nominal or face amount used to calculate payments on the derivative liability.

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Derivatives (Details) - Foreign Currency Forward £ in Millions, $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2019 GBP (£)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 GBP (£)
Derivative [Line Items]
Notional amount \| £			£ 46.0		£ 46.0
Loss on derivative instruments	$ 2.8	$ 1.5
Other Current Liabilities
Derivative [Line Items]
Derivative liability	$ 2.3	$ 2.3		$ 3.8