Share-Based Compensation Share-based compensation expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Expense [Line Items]
Share-based Compensation	$ 1.7	$ 11.1	$ 7.7	$ 19.1
Stock Options [Member]
Share-based Compensation Expense [Line Items]
Share-based Compensation	0.6	0.5	1.2	1.2
Restricted Share Awards [Member]
Share-based Compensation Expense [Line Items]
Share-based Compensation	6.0	5.7	13.3	12.2
Performance Share Units [Member]
Share-based Compensation Expense [Line Items]
Share-based Compensation	(4.9)	4.8	(6.8)	5.6
Restricted Share Units (RSUs) [Member]
Share-based Compensation Expense [Line Items]
Share-based Compensation	$ 0.0	$ 0.1	$ 0.0	$ 0.1