Income (Loss) per Share - Computation of Basic and Diluted Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income (loss)	$ 14.7	$ 89.4
Less: Restricted stock dividends, Basic	(0.2)	(0.2)
Less: Restricted stock dividends, Diluted	(0.2)	(0.2)
Net (loss) income available to stockholders, Basic	14.5	89.2
Net (loss) income available to stockholders, Diluted	$ 14.5	$ 89.2
Denominator:
Weighted average shares outstanding - basic (in shares)	114.9	108.3
Performance-based restricted stock and units (in shares)	0.2	0.5
Weighted average shares outstanding- diluted (in shares)	115.1	108.8
EPS:
Income (loss) per share - basic (in dollars per share)	$ 0.13	$ 0.82
Effect of dilutive shares:
Income (loss) per share - diluted (in dollars per share)	$ 0.13	$ 0.82