Shareholders' Equity - Summary of Stock-Based Compensation Expense by Type of Award (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ (0.4)	$ 22.0	$ 12.9	$ 8.6
SARS
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	(1.4)	9.3	2.2	1.8
Restricted Stock, Service-Based
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.3	4.1	3.6	5.6
Restricted Stock, Performance-Based
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.6	6.8	5.7	0.1
Employee Stock Purchase Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.0	0.6	0.5	0.3
Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 0.1	$ 1.2	$ 0.9	$ 0.8