Earnings Per Share - EPS Calculation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net (loss)/income	$ (1.9)	$ 16.9
Denominator:
Weighted average common shares outstanding - basic (in shares)	146.1	146.0
Weighted average additional shares assuming conversion of potential common shares (in shares)	0.0	0.5
Weighted average common shares outstanding – diluted (in shares)	146.1	146.5
Basic earnings per common share:
Net (loss)/income per weighted average share - basic (in dollars per share)	$ (0.01)	$ 0.12
Diluted earnings per common share:
Net (loss)/income per weighted average share - diluted (in dollars per share)	$ (0.01)	$ 0.12