Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at Sep. 30, 2020	$ 1,271.5	$ 1.0	$ 1,467.8	$ (187.9)	$ (6.9)	$ (2.5)
Balance, Shares at Sep. 30, 2020		104.9
Net income (loss)	(5.7)			(5.7)
Other comprehensive income, net of tax	5.4				5.4
Capital contributions and issuance of common stock	1.5	$ 0.1	1.4
Capital contributions and issuance of common stock, Shares		0.3
Equity-based compensation	10.2		10.2
Repurchase of common stock and distributions	1.1					1.1
Balance at Mar. 31, 2021	1,281.8	$ 1.1	1,479.4	(193.6)	(1.5)	(3.6)
Balance, Shares at Mar. 31, 2021		105.2
Balance at Dec. 31, 2020	1,268.7	$ 1.1	1,474.4	(199.9)	(3.3)	(3.6)
Balance, Shares at Dec. 31, 2020		105.1
Net income (loss)	6.3			6.3
Other comprehensive income, net of tax	1.8				1.8
Capital contributions and issuance of common stock	(0.3)		(0.3)
Capital contributions and issuance of common stock, Shares		0.1
Equity-based compensation	5.3		5.3
Balance at Mar. 31, 2021	1,281.8	$ 1.1	1,479.4	(193.6)	(1.5)	(3.6)
Balance, Shares at Mar. 31, 2021		105.2
Balance at Sep. 30, 2021	1,342.7	$ 1.1	1,489.1	(141.6)	(1.5)	(4.4)
Balance, Shares at Sep. 30, 2021		105.2
Net income (loss)	(12.1)			(12.1)
Other comprehensive income, net of tax	2.9				2.9
Capital contributions and issuance of common stock	1.5		1.5
Capital contributions and issuance of common stock, Shares		0.5
Equity-based compensation	9.3		9.3
Repurchase of common stock and distributions	(90.8)					(90.8)
Balance at Mar. 31, 2022	1,253.5	$ 1.1	1,499.9	(153.7)	1.4	(95.2)
Balance, Shares at Mar. 31, 2022		105.7
Balance at Dec. 31, 2021	1,334.5	$ 1.1	1,495.3	(154.4)	(1.0)	(6.5)
Balance, Shares at Dec. 31, 2021		105.7
Net income (loss)	0.7			0.7
Other comprehensive income, net of tax	2.4				2.4
Equity-based compensation	4.6		4.6
Repurchase of common stock and distributions	88.7					88.7
Balance at Mar. 31, 2022	$ 1,253.5	$ 1.1	$ 1,499.9	$ (153.7)	$ 1.4	$ (95.2)
Balance, Shares at Mar. 31, 2022		105.7