Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	APIC [Member]	[1]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	AOCI [Member]	[2]
Balance at Sep. 30, 2019	$ 1,862.3		$ 0.7	$ 1,083.0		$ 799.2		$ (20.6)
Balance (in shares) at Sep. 30, 2019			68,600,000
Issuance of common stock, net of shares withheld for taxes	(1.2)			(1.2)
Issuance of common stock, net of shares withheld for taxes (Shares)			300,000
Stock-based compensation	13.3			13.3
Other comprehensive income (loss)	(16.9)							(16.9)
Net income (loss)	(152.8)					(152.8)
Dividends on Preferred Stock	(18.0)					(18.0)
Balance at Jun. 30, 2020	1,686.7		$ 0.7	1,095.1		628.4		(37.5)
Balance (in shares) at Jun. 30, 2020			68,900,000
Balance at Mar. 31, 2020	1,694.2		$ 0.7	1,091.5		641.1		(39.1)
Balance (in shares) at Mar. 31, 2020			68,800,000
Issuance of common stock, net of shares withheld for taxes	0.1			0.1
Stock-based compensation	3.5			3.5
Other comprehensive income (loss)	1.6							1.6
Net income (loss)	(6.7)					(6.7)
Dividends on Preferred Stock	(6.0)					(6.0)
Balance at Jun. 30, 2020	1,686.7		$ 0.7	1,095.1		628.4		(37.5)
Balance (in shares) at Jun. 30, 2020			68,900,000
Balance at Sep. 30, 2020	1,760.9	$ (4.3)	$ 0.7	1,100.6		694.3	$ (4.3)	(34.7)
Accounting Standards Update [Extensible Enumeration]		us-gaap:AccountingStandardsUpdate201613Member					us-gaap:AccountingStandardsUpdate201613Member
Balance (in shares) at Sep. 30, 2020			69,000,000.0
Issuance of common stock, net of shares withheld for taxes	20.3			20.3
Issuance of common stock, net of shares withheld for taxes (Shares)			1,000,000.0
Stock-based compensation	17.6			17.6
Other comprehensive income (loss)	12.2							12.2
Net income (loss)	(150.3)					(150.3)
Dividends on Preferred Stock	(18.0)					(18.0)
Balance at Jun. 30, 2021	1,638.4		$ 0.7	1,138.5		521.7		(22.5)
Balance (in shares) at Jun. 30, 2021			70,000,000.0
Balance at Mar. 31, 2021	1,553.3		$ 0.7	1,126.2		451.2		(24.8)
Accounting Standards Update [Extensible Enumeration]		us-gaap:AccountingStandardsUpdate201613Member					us-gaap:AccountingStandardsUpdate201613Member
Balance (in shares) at Mar. 31, 2021			69,800,000
Issuance of common stock, net of shares withheld for taxes	6.9			6.9
Issuance of common stock, net of shares withheld for taxes (Shares)			200,000
Stock-based compensation	5.4			5.4
Other comprehensive income (loss)	2.3							2.3
Net income (loss)	76.5					76.5
Dividends on Preferred Stock	(6.0)					(6.0)
Balance at Jun. 30, 2021	$ 1,638.4		$ 0.7	$ 1,138.5		$ 521.7		$ (22.5)
Balance (in shares) at Jun. 30, 2021			70,000,000.0

[1] Additional Paid-in Capital (“APIC”).

[2] Accumulated Other Comprehensive Income (Loss) ("AOCI").