Share Plans - Schedule of Share-based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 5.1	$ 6.2	$ 16.4	$ 32.2
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	2.4	2.9	6.7	14.4
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	1.3	1.9	3.5	8.3
Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 1.4	$ 1.4	$ 6.2	$ 9.5