Stock-based Payments - Summary of Performance-Based Options (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Exercise Price per Share
Expected option life	3 years
Time-Based Options
Number of Options
Outstanding, beginning balance (in shares)	3,300,000	3,500,000	2,200,000
Granted (in shares)	0	200,000	100,000
Forfeited (in shares)	(100,000)	(100,000)	(100,000)
Outstanding, ending balance (in shares)	2,600,000	3,300,000	3,500,000	2,200,000
Exercisable as of December 31, 2018 (in shares)	(1,900,000)
Weighted Average Exercise Price per Share
Outstanding, beginning balance (USD per share)	$ 11.23	$ 10.88	$ 10.65
Granted (USD per share)	0	17.00	17.00
Forfeited (USD per share)	11.19	12.58	11.79
Outstanding, ending balance (USD per share)	11.51	$ 11.23	$ 10.88	$ 10.65
Weighted average exercise price per share, exercisable (USD per share)	$ 10.67
Weighted average remaining contractual term, outstanding	5 years 10 months 24 days	6 years 9 months 18 days	8 years 6 months	8 years 7 months 6 days
Weighted average remaining contractual term, exercisable	5 years 8 months 12 days
Outstanding, Aggregate Intrinsic Value	$ 24.3	$ 11.8	$ 13.8	$ 14.2
Expected option life	0 years	6 years 4 months 24 days	5 years 6 months
Exercisable aggregate intrinsic value	$ 19.0
Options modified (in shares)			1,300,000
Performance-Based Options
Number of Options
Outstanding, beginning balance (in shares)	1,500,000	1,600,000	3,600,000
Granted (in shares)	0	100,000	100,000
Modified (in shares)			(1,300,000)
Forfeited (in shares)	(100,000)	(200,000)	(800,000)
Outstanding, ending balance (in shares)	1,400,000	1,500,000	1,600,000	3,600,000
Exercisable as of December 31, 2018 (in shares)	0
Weighted Average Exercise Price per Share
Outstanding, beginning balance (USD per share)	$ 11.48	$ 11.23	$ 10.90
Granted (USD per share)	0	17.00	17.00
Modified (USD per share)	9.13		11.06
Forfeited (USD per share)	10.87	11.98	10.50
Outstanding, ending balance (USD per share)	11.64	$ 11.48	$ 11.23	$ 10.90
Weighted average exercise price per share, exercisable (USD per share)	$ 0.00
Weighted average remaining contractual term, outstanding	5 years 10 months 24 days	6 years 10 months 24 days	7 years 9 months 18 days	8 years 7 months 6 days
Weighted average remaining contractual term, exercisable	0 years
Outstanding, Aggregate Intrinsic Value	$ 12.0	$ 4.5	$ 9.5	$ 22.2
Expected option life		1 year 1 month 6 days	1 year 2 months 12 days
Exercisable aggregate intrinsic value	$ 0.0