Share-Based Compensation Share-based compensation expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	$ 4.1	$ 2.7	$ 21.0	$ 26.1
Stock Options [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	0.0	0.2	0.3	0.9
Performance Share Units [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	(0.9)	(2.9)	4.6	4.1
Restricted Shares [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	5.0	5.3	15.9	20.9
Restricted Share Units (RSUs) [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	0.0	0.1	0.2	0.2
Net gain (loss) from asset sales [Member]
Share-based Compensation Expense [Line Items]
Accelerated Share Based Compensation	0.0	2.2	1.5	2.2
General and Administrative Expense [Member]
Share-based Compensation Expense [Line Items]
Accelerated Share Based Compensation	1.6	1.0	9.8	5.0
Total [Member]
Share-based Compensation Expense [Line Items]
Accelerated Share Based Compensation	$ 1.6	$ 3.2	$ 11.3	$ 7.2