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Derivatives (Details) - Foreign Currency Forward
£ in Millions, $ in Millions
3 Months Ended
Mar. 31, 2019
USD ($)
Mar. 31, 2019
GBP (£)
Dec. 31, 2018
USD ($)
Dec. 31, 2018
GBP (£)
Derivative [Line Items]        
Notional amount | £   £ 46.0   £ 46.0
Gain on derivative instruments $ 1.2      
Other Current Liabilities        
Derivative [Line Items]        
Derivative liability $ 0.7   $ 3.8