Share-Based Compensation Share-based compensation expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	$ 3.9	$ 11.7
Accelerated Share Based Compensation	0.2	8.4
Stock Options [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	0.0	0.3
Restricted Shares [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	3.3	6.1
Restricted Cash Awards [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	0.2	0.0
Performance Share Units [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	0.4	5.2
Restricted Share Units (RSUs) [Member]
Share-based Compensation Expense [Line Items]
Allocated Share-based Compensation Expense	$ 0.0	0.1
Net gain (loss) from asset sales [Member]
Share-based Compensation Expense [Line Items]
Accelerated Share Based Compensation		1.5
General and Administrative Expense [Member]
Share-based Compensation Expense [Line Items]
Accelerated Share Based Compensation		$ 6.9