Equity - Reclassification Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Costs of sales and services	$ 69.8			$ 69.4			$ 178.4	$ 215.2
Total before tax	15.3			(13.8)			19.7	(52.9)
Net (loss)/income	11.8	$ 0.2	$ 1.9	(18.0)	$ (15.5)	$ (16.9)	13.9	(50.4)
Income tax (benefit)/expense	(3.5)			(4.2)			(5.8)	2.5
Amounts Reclassified from Acccumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(0.2)			(0.4)			(0.2)	(1.1)
Net (loss)/income	(0.2)			(0.4)			(0.2)	(1.1)
Income tax (benefit)/expense				0.1				0.1
Foreign currency contracts | Derivative instruments | Amounts Reclassified from Acccumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Costs of sales and services	$ (0.2)			$ (0.4)			$ (0.2)	$ (1.1)