Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	APIC	[1]	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	AOCI	[2]
Beginning balance (in shares) at Sep. 30, 2020			69.0
Beginning balance at Sep. 30, 2020	$ 1,760.9	$ (4.3)	$ 0.7	$ 1,100.6		$ 694.3	$ (4.3)	$ (34.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of shares withheld for taxes (in shares)			1.1
Issuance of common stock, net of shares withheld for taxes	21.8			21.8
Stock-based compensation	22.6			22.6
Other comprehensive income (loss)	11.3							11.3
Net income (loss)	(45.5)					(45.5)
Dividends on Preferred Stock	(24.0)					(24.0)
Ending balance (in shares) at Sep. 30, 2021			70.1
Ending balance at Sep. 30, 2021	1,742.8		$ 0.7	1,145.0		620.5		(23.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of shares withheld for taxes (in shares)			0.3
Issuance of common stock, net of shares withheld for taxes	0.8			0.8
Stock-based compensation	2.8			2.8
Other comprehensive income (loss)	4.0							4.0
Net income (loss)	68.0					68.0
Dividends on Preferred Stock	(6.0)					(6.0)
Ending balance (in shares) at Dec. 31, 2021			70.4
Ending balance at Dec. 31, 2021	1,812.4		$ 0.7	1,148.6		682.5		(19.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of shares withheld for taxes (in shares)			0.7
Issuance of common stock, net of shares withheld for taxes	$ 11.0			11.0
Repurchase and retired of common stock, net (in shares)	(6.8)		(6.9)
Repurchase and retirement of common stock, net	$ (388.2)		$ (0.1)			(388.1)
Stock-based compensation	27.6			27.6
Other comprehensive income (loss)	6.9							6.9
Net income (loss)	458.4					458.4
Dividends on Preferred Stock	(24.0)					(24.0)
Ending balance (in shares) at Dec. 31, 2022			64.2
Ending balance at Dec. 31, 2022	1,904.1		$ 0.6	1,187.2		728.8		(12.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of shares withheld for taxes (in shares)			0.7
Issuance of common stock, net of shares withheld for taxes	$ (1.1)			(1.1)
Repurchase and retired of common stock, net (in shares)	(1.6)		(1.6)
Repurchase and retirement of common stock, net	$ (111.5)					(111.5)
Repurchase of Preferred Stock, net	(414.6)					(414.6)
Stock-based compensation	28.0			28.0
Other comprehensive income (loss)	(1.8)							(1.8)
Proceeds from disgorgement of short-swing profits, net of tax	4.3			4.3
Net income (loss)	435.0					435.0
Dividends on Preferred Stock	(18.9)					(18.9)
Ending balance (in shares) at Dec. 31, 2023			63.3
Ending balance at Dec. 31, 2023	$ 1,823.5		$ 0.6	$ 1,218.4		$ 618.8		$ (14.3)

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

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