Share-Based Compensation Schedule of Share-based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Expense [Line Items]
Share-based compensation expense	$ 36.9	$ 22.4	$ 35.6
Accelerated Share Based Compensation	11.0
Stock Options [Member]
Share-based Compensation Expense [Line Items]
Share-based compensation expense	1.2	2.3	2.3
Restricted Share Awards [Member]
Share-based Compensation Expense [Line Items]
Share-based compensation expense	27.5	24.6	23.7
Performance Share Units [Member]
Share-based Compensation Expense [Line Items]
Share-based compensation expense	8.1	(4.5)	9.4
Restricted Share Units (RSUs) [Member]
Share-based Compensation Expense [Line Items]
Share-based compensation expense	0.1	$ 0.0	$ 0.2
General and administrative expense [Member]
Share-based Compensation Expense [Line Items]
Accelerated Share Based Compensation	8.8
Net gain (loss) from asset sales, inclusive of restructuring costs [Member]
Share-based Compensation Expense [Line Items]
Accelerated Share Based Compensation	$ 2.2