Net Income (Loss) Per Common Share - Summary of Earnings Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic net income (loss) per common share:
Net income (loss)	$ 2.2	$ (14.0)	$ (1.0)	$ 42.4	$ (11.8)	$ 41.4
Weighted average common shares outstanding - Basic (in shares)	84.1		83.7		84.0	83.7
Basic net income (loss) per common share	$ 0.03		$ (0.01)		$ (0.14)	$ 0.49
Diluted net income (loss) per common share:
Net income (loss)	$ 2.2		$ (1.0)		$ (11.8)	$ 41.4
Weighted average common shares outstanding - Basic (in shares)	84.1		83.7		84.0	83.7
Plus incremental shares from assumed conversions:
Weighted average common shares outstanding - Dilutive (in shares)	84.7		83.7		84.0	84.1
Diluted net income (loss) per common share	$ 0.03		$ (0.01)		$ (0.14)	$ 0.49
Restricted Stock Units
Plus incremental shares from assumed conversions:
Incremental shares from assumed conversions	0.3					0.2
Stock Options
Plus incremental shares from assumed conversions:
Incremental shares from assumed conversions	0.3					0.2