Equity - Reclassification Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Costs of sales and services	$ 53.9	$ 65.6
Total before tax	(2.2)	21.0
Income tax (benefit)/expense	(0.3)	4.1
Net (loss)/income	$ (1.9)	16.9
Amounts Reclassified from Accumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		0.4
Income tax (benefit)/expense		0.1
Net (loss)/income		0.4
Foreign currency contracts | Derivative instruments | Amounts Reclassified from Accumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Costs of sales and services		$ (0.4)