Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	APIC [Member]	[1]	Retained Earnings [Member]	AOCI [Member]	[2]
Balance at Sep. 30, 2017	$ 1,781.8	$ 0.7	$ 1,047.5		$ 748.2	$ (14.6)
Balance (in shares) at Sep. 30, 2017		67,700,000
Issuance of common stock, net of shares withheld for taxes	3.5		3.5
Issuance of common stock, net of shares withheld for taxes (Shares)		400,000
Issuance costs related to secondary offering of common stock	(0.5)		(0.5)
Stock-based compensation	16.5		16.5
Other comprehensive income (loss)	(2.7)					(2.7)
Net income (loss)	98.6				98.6
Dividends on Preferred Stock	(13.0)				(13.0)
Balance at Sep. 30, 2018	1,884.2	$ 0.7	1,067.0		833.8	(17.3)
Balance (in shares) at Sep. 30, 2018		68,100,000
Issuance of common stock, net of shares withheld for taxes	(0.4)		(0.4)
Issuance of common stock, net of shares withheld for taxes (Shares)		400,000
Stock-based compensation	16.4		16.4
Other comprehensive income (loss)	(3.3)					(3.3)
Net income (loss)	(10.6)				(10.6)
Dividends on Preferred Stock	(24.0)				(24.0)
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	0.4		0.4
Issuance of common stock, net of shares withheld for taxes (Shares)		400,000
Stock-based compensation	17.2		17.2
Other comprehensive income (loss)	(14.1)					(14.1)
Net income (loss)	(80.9)				(80.9)
Dividends on Preferred Stock	(24.0)				(24.0)
Balance at Sep. 30, 2020	$ 1,760.9	$ 0.7	$ 1,100.6		$ 694.3	$ (34.7)
Balance (in shares) at Sep. 30, 2020		69,000,000.0

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

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