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Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income (loss)		$ (34.6)	$ (65.0)	$ (0.3)	$ (20.7)	$ 19.4	$ (20.7)	$ (20.3)	$ (80.8)	$ (66.2)	$ 48.6
Amount allocated to common stockholders									100.00%	100.00%	92.00%
Basic and Diluted EPS:
Net income (loss) allocated to common stockholders	$ (4.8)	$ (34.6)	$ (65.0)	$ (0.3)	$ (20.7)	$ 17.9	$ (20.7)	$ (20.3)	$ (80.8)	$ (66.2)	$ 44.7
Shares outstanding, basic and diluted (in shares)									88.8	87.6	88.0
Basic and diluted (in dollars per share)									$ (0.91)	$ (0.76)	$ 0.51
EPS:
Net loss allocated to common stockholders, basic											$ 44.7
Shares outstanding, basic (in shares)											87.3
Basic (in dollars per share)	$ (0.05)	$ (0.39)	$ (0.74)	$ 0.00	$ (0.23)	$ 0.20	$ (0.23)	$ (0.23)			$ 0.51

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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