Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Treasury Stock	Treasury Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Additional Paid-In Capital	Additional Paid-In Capital Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated other comprehensive (loss)	Accumulated other comprehensive (loss) Cumulative Effect, Period of Adoption, Adjusted Balance
Beginning Balance (in shares) at Dec. 31, 2018			123,353,656		12,811,755
Beginning Balance at Dec. 31, 2018	$ 6.3		$ 1.2		$ (62.6)		$ 361.0		$ (289.8)			$ (3.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Share-based compensation expense	$ 18.8						18.8
Issuance of common stock related to share-based compensation plans (in shares)			1,812,993
Exercise of vested stock options (in shares)	2,640,897		2,640,897
Exercise of vested stock options	$ 13.7		$ 0.1				13.6
Dividends paid/accrued on preferred stock	(20.7)						(20.7)
Acquisition of treasury stock related to equity award plans (in shares)					(973,303)
Acquisition of treasury stock related to equity award plans	(11.0)				$ (11.0)
Forfeitures (in shares)					(1,208)
Net change on derivatives designated as cash flow hedges, net of tax	(0.2)											(0.2)
Foreign currency translation adjustment	(0.8)											(0.8)
Net income	12.0								12.0
Ending Balance (in shares) at Dec. 31, 2019			127,807,546	127,807,546	13,786,266	13,786,266
Ending Balance at Dec. 31, 2019	18.1	$ 17.3	$ 1.3	$ 1.3	$ (73.6)	$ (73.6)	372.7	$ 372.7	(277.8)	$ (0.8)	$ (278.6)	(4.5)	$ (4.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	24.2						24.2
Issuance of common stock related to share-based compensation plans (in shares)			6,848,859
Issuance of common stock related to share-based compensation plans	$ 0.0		$ 0.1				(0.1)
Exercise of vested stock options (in shares)	3,156,154		3,156,154
Exercise of vested stock options	$ 19.3						19.3
Dividends paid/accrued on preferred stock	(22.4)						(22.4)
Acquisition of treasury stock related to equity award plans (in shares)					(2,882,255)
Acquisition of treasury stock related to equity award plans	(65.6)				$ (65.6)
Net change on derivatives designated as cash flow hedges, net of tax	(1.7)											(1.7)
Foreign currency translation adjustment	(0.3)											(0.3)
Net income	117.1								117.1
Ending Balance (in shares) at Dec. 31, 2020			137,812,559		16,668,521
Ending Balance at Dec. 31, 2020	87.9		$ 1.4		$ (139.2)		393.7		(161.5)			(6.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	$ 74.9						74.9
Issuance of common stock related to share-based compensation plans (in shares)			2,325,918
Issuance of common stock (in shares)	324,212
Issuance of common stock	$ 7.0						7.0
Exercise of vested stock options (in shares)	1,819,039		1,819,039
Exercise of vested stock options	$ 8.0						8.0
Acquisition of treasury stock related to equity award plans (in shares)					(796,908)
Acquisition of treasury stock related to equity award plans	(19.1)				$ (19.1)
Repurchases of common stock (in shares)					(2,629,257)
Repurchases of common stock	(56.9)				$ (56.9)
Net change on derivatives designated as cash flow hedges, net of tax	2.1											2.1
Foreign currency translation adjustment	(0.9)											(0.9)
Conversion of preferred shares (in shares)			117,706,400
Conversion of preferred shares	251.5		$ 1.2				250.3
Inducement dividend	(592.3)						(592.3)
Issuance of common stock related to inducement (in shares)			21,582,800
Issuance of common stock related to inducement	487.3		$ 0.2				487.1
Exercise of warrants pursuant to cashless provisions (in shares)			16,750,000
Exercise of warrants pursuant to cashless provisions	0.0		$ 0.2				(0.2)
Net income	97.2								97.2
Ending Balance (in shares) at Dec. 31, 2021			298,320,928		20,094,686
Ending Balance at Dec. 31, 2021	$ 346.7		$ 3.0		$ (215.2)		$ 628.5		$ (64.3)			$ (5.3)