Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 3.4	$ 2.8	$ 8.9	$ 8.8
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	0.7	0.7	2.0	2.4
Time-based restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	1.8	0.6	4.2	3.2
Performance-based restricted share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	0.8	1.4	2.5	3.1
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 0.1	$ 0.1	$ 0.2	$ 0.1