Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Aug. 30, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 3.4	$ 3.1	$ 10.2	$ 5.4
Stock appreciation rights
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.0	1.5	2.4	1.9
Stock options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.3	0.1	0.7	0.3
Restricted shares, service based
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1.2	0.8	2.4	1.6
Restricted shares, performance based
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1.8	0.6	4.4	1.4
Employee stock purchase plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 0.1	$ 0.1	$ 0.3	$ 0.2
Common Stock | Minimum
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share price (in USD per share)					$ 22
Common Stock | Maximum
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share price (in USD per share)					$ 27