Stock-Based Compensation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 0.5	$ 5.5	$ 10.6	$ 13.2
Stock Appreciation Rights
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	(3.5)	0.6	(3.8)	(1.3)
Stock options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.0	0.1	0.0	0.3
Restricted stock and restricted stock units, service based
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1.5	1.5	4.5	4.7
Restricted stock and restricted stock units, performance based
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2.5	3.0	9.4	8.7
Employee stock purchase plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 0.0	$ 0.3	$ 0.5	$ 0.8