Net Income (Loss) Per Share - Components and Calculation of Basic and Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Dec. 31, 2021		Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Numerator:
Net income (loss) from continuing operations		$ 68.1		$ 104.5	$ 79.8	$ (10.5)	$ 47.4
Dividends on Preferred Stock		(6.0)					(6.0)
Undistributed income from continuing operations allocated to participating securities		(7.5)
Net income (loss) from continuing operations attributable to common stockholders - Basic and Diluted		54.6					41.4
Net income (loss) from discontinued operations attributable to common stockholders - Basic and Diluted		(0.1)					(267.9)
Net income (loss) attributable to common stockholders - Basic and Diluted		$ 54.5					$ (226.5)
Denominator:
Weighted-average common shares outstanding - Basic	[1]	70,300,000					69,200,000
Effect of common share equivalents		1,200,000					800,000
Weighted-average common shares outstanding - Diluted	[1]	71,500,000					70,000,000.0
Net income (loss) per share:
Basic - Continuing operations		$ 0.78	[1]	$ 1.23	$ 0.93	$ (0.24)	$ 0.60	[1]
Basic - Discontinued operations	[1]						(3.87)
Basic net income (loss) per share		0.78	[1]	1.24	0.89	(0.18)	(3.27)	[1]
Diluted - Continuing operations		0.76	[1]	1.21	0.91	(0.24)	0.59	[1]
Diluted - Discontinued operations	[1]						(3.83)
Diluted net income (loss) per share		$ 0.76	[1]	$ 1.22	$ 0.87	$ (0.18)	$ (3.24)	[1]

[1] See Note 6 for detailed calculations and further discussion.