Earnings (Loss) per Common Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings (Loss) per Common Share
Loss from continuing operations, basic	$ (68.6)	$ (108.3)	$ (82.4)
Loss from continuing operations, diluted	(68.6)	(108.3)	(82.4)
Income from discontinued operations, basic	839.1	122.7	118.8
Income from discontinued operations, diluted	839.1	122.7	118.8
Net income, basic	770.5	14.4	36.4
Net income, diluted	$ 770.5	$ 14.4	$ 36.4
Basic weighted-average shares	82,720,934	81,561,707	80,713,926
Diluted weighted-average shares	82,720,934	81,561,707	80,713,926
Basic and diluted (loss) per common share - continuing operations
Basic (in dollars per share)	$ (0.83)	$ (1.33)	$ (1.02)
Diluted (in dollars per share)	(0.83)	(1.33)	(1.02)
Basic and diluted earnings per common share - discontinued operations
Basic (in dollars per share)	10.14	1.51	1.47
Diluted (in dollars per share)	10.14	1.51	1.47
Basic and diluted earnings per common share
Basic (in dollars per share)	9.31	0.18	0.45
Diluted (in dollars per share)	$ 9.31	$ 0.18	$ 0.45