Consolidated Statement Of Stockholders' Equity - USD ($) $ in Millions	Total	Common stock	Accumulated deficit	Accumulated deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated other comprehensive income (loss)	Noncontrolling Interest [Member]	Additional Paid-in Capital [Member]
Other comprehensive income (loss), net of tax					$ 4.0
Common stock, dividends, per share, declared	$ 0.0525
Balance at Sep. 30, 2019		$ 1.6	$ (786.2)		(36.0)	$ 2.2	$ 1,410.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared							8.3
Stock-based compensation							1.3
Shares retained for employee taxes							0.7
Stock issued under stock compensation plans	$ 0.0						1.4
Net income (loss)	10.3
Balance at Dec. 31, 2019		1.6	(775.9)		(32.0)	0.0	1,401.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from (Payments to) Noncontrolling Interests						(2.2)
Adjustments to Additional paid in capital, other							(3.2)
Acquisition of joint venture partner's interest	5.2
Stockholders' Equity Attributable to Parent	595.0			$ 0.0
Common stock, value, issued	1.6
Other comprehensive income (loss), net of tax	$ 5.0				5.0
Common stock, dividends, per share, declared	$ 0.0550
Balance at Sep. 30, 2020	$ 640.7	1.6	(714.2)		(24.7)	0.0	1,378.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared							8.7
Stock-based compensation							1.9
Shares retained for employee taxes							0.9
Stock issued under stock compensation plans	0.0						0.6
Net income (loss)	16.7
Balance at Dec. 31, 2020	655.2	$ 1.6	$ (697.6)		$ (19.7)	0.0	1,370.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional paid in capital, other							$ 0.0
Acquisition of joint venture partner's interest	0.0
Noncontrolling interest, decrease from distributions to noncontrolling interest holders						$ 0.0
Common stock, value, issued	1.6
Stockholders' Equity Attributable to Parent	$ 655.2			$ (0.1)