Net Income (loss) per common share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net income (loss)	$ (223.8)	$ 230.9	$ 305.1
Denominator:
Weighted-average number of shares-basic (in shares)	50.1	53.5	52.7
Dilutive securities-equity awards (in shares)	0.0	0.6	1.1
Weighted-average number of shares-diluted (in shares)	50.1	54.1	53.8
Net income (loss) per common share - basic (in dollars per share)	$ (4.47)	$ 4.32	$ 5.79
Net income (loss) per common share - diluted (in dollars per share)	$ (4.47)	$ 4.27	$ 5.67
Anti-dilutive stock awards (in shares)	2.8	1.0	0.0