Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	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, 2019				127,807,546	127,807,546	13,786,266	13,786,266
Beginning Balance at Dec. 31, 2019	$ 18.1	$ (0.8)	$ 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	4.8							4.8
Issuance of common stock related to share-based compensation plans (in shares)				1,720
Exercise of vested stock options (in shares)				553,520
Exercise of vested stock options	3.1							3.1
Dividends paid/accrued	(5.4)							(5.4)
Acquisition of treasury stock related to share-based compensation plans (in shares)						(545)
Net change on derivatives designated as cash flow hedges, net of tax	(4.4)												(4.4)
Foreign currency translation adjustments	(2.1)												(2.1)
Net income	18.2									18.2
Ending Balance (in shares) at Mar. 31, 2020				128,362,786		13,786,811
Ending Balance at Mar. 31, 2020	31.5			$ 1.3		$ (73.6)		375.2		(260.4)			(11.0)
Beginning Balance (in shares) at Dec. 31, 2019				127,807,546	127,807,546	13,786,266	13,786,266
Beginning Balance at Dec. 31, 2019	$ 18.1	$ (0.8)	$ 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]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Net change on derivatives designated as cash flow hedges, net of tax	$ (2.5)
Foreign currency translation adjustments	(0.9)
Net income	38.5
Ending Balance (in shares) at Sep. 30, 2020				130,412,966		13,919,939
Ending Balance at Sep. 30, 2020	62.5			$ 1.3		$ (74.8)		384.0		(240.1)			(7.9)
Beginning Balance (in shares) at Mar. 31, 2020				128,362,786		13,786,811
Beginning Balance at Mar. 31, 2020	31.5			$ 1.3		$ (73.6)		375.2		(260.4)			(11.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	4.4							4.4
Issuance of common stock related to share-based compensation plans (in shares)				463,038
Exercise of vested stock options (in shares)				464,136
Exercise of vested stock options	1.2							1.2
Dividends paid/accrued	(5.6)							(5.6)
Acquisition of treasury stock related to share-based compensation plans (in shares)						(128,361)
Acquisition of treasury stock related to share-based compensation plans	(1.1)					$ (1.1)
Net change on derivatives designated as cash flow hedges, net of tax	0.8												0.8
Foreign currency translation adjustments	(0.2)												(0.2)
Net income	15.1									15.1
Ending Balance (in shares) at Jun. 30, 2020				129,289,960		13,915,172
Ending Balance at Jun. 30, 2020	$ 46.1			$ 1.3		$ (74.7)		375.2		(245.3)			(10.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Share-based compensation expense	$ 6.8							6.8
Issuance of common stock related to share-based compensation plans (in shares)				14,015
Exercise of vested stock options (in shares)				1,108,991
Exercise of vested stock options	7.6							7.6
Dividends paid/accrued	(5.6)							(5.6)
Acquisition of treasury stock related to share-based compensation plans (in shares)						(4,767)
Acquisition of treasury stock related to share-based compensation plans	(0.1)					$ (0.1)
Net change on derivatives designated as cash flow hedges, net of tax	1.1												1.1
Foreign currency translation adjustments	1.4												1.4
Net income	5.2									5.2
Ending Balance (in shares) at Sep. 30, 2020				130,412,966		13,919,939
Ending Balance at Sep. 30, 2020	62.5			$ 1.3		$ (74.8)		384.0		(240.1)			(7.9)
Beginning Balance (in shares) at Dec. 31, 2020				137,812,559		16,668,521
Beginning 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	12.8							12.8
Issuance of common stock related to share-based compensation plans (in shares)				6,497
Issuance of common stock (in shares)				324,212
Issuance of common stock	7.0							7.0
Exercise of vested stock options (in shares)				539,795
Exercise of vested stock options	3.5							3.5
Acquisition of treasury stock related to share-based compensation plans (in shares)						(2,201)
Net change on derivatives designated as cash flow hedges, net of tax	0.5												0.5
Foreign currency translation adjustments	(0.4)												(0.4)
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
Net income	25.8									25.8
Ending Balance (in shares) at Mar. 31, 2021				277,972,263		16,670,722
Ending Balance at Mar. 31, 2021	283.6			$ 2.8		$ (139.2)		562.1		(135.7)			(6.4)
Beginning Balance (in shares) at Dec. 31, 2020				137,812,559		16,668,521
Beginning Balance at Dec. 31, 2020	$ 87.9			$ 1.4		$ (139.2)		393.7		(161.5)			(6.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of vested stock options (in shares)	1,108,632
Net change on derivatives designated as cash flow hedges, net of tax	$ 0.9
Foreign currency translation adjustments	(1.0)
Net income	61.2
Ending Balance (in shares) at Sep. 30, 2021				295,885,508		18,393,186
Ending Balance at Sep. 30, 2021	334.1			$ 3.0		$ (175.7)		613.7		(100.3)			(6.6)
Beginning Balance (in shares) at Mar. 31, 2021				277,972,263		16,670,722
Beginning Balance at Mar. 31, 2021	283.6			$ 2.8		$ (139.2)		562.1		(135.7)			(6.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	24.0							24.0
Issuance of common stock related to share-based compensation plans (in shares)				539,884
Exercise of vested stock options (in shares)				396,250
Exercise of vested stock options	1.3							1.3
Acquisition of treasury stock related to share-based compensation plans (in shares)						(167,832)
Acquisition of treasury stock related to share-based compensation plans	(4.5)					$ (4.5)
Net change on derivatives designated as cash flow hedges, net of tax	(0.1)												(0.1)
Foreign currency translation adjustments	(0.6)												(0.6)
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	18.4									18.4
Ending Balance (in shares) at Jun. 30, 2021				295,658,397		16,838,554
Ending Balance at Jun. 30, 2021	322.1			$ 3.0		$ (143.7)		587.2		(117.3)			(7.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	25.8							25.8
Issuance of common stock related to share-based compensation plans (in shares)				54,524
Exercise of vested stock options (in shares)				172,587
Exercise of vested stock options	0.7							0.7
Acquisition of treasury stock related to share-based compensation plans (in shares)						(16,555)
Acquisition of treasury stock related to share-based compensation plans	$ (0.3)					$ (0.3)
Repurchases of common stock (in shares)	(1,538,077)
Repurchases of common stock	$ (31.7)
Net change on derivatives designated as cash flow hedges, net of tax	0.5												0.5
Foreign currency translation adjustments	0.0
Net income	17.0									17.0
Ending Balance (in shares) at Sep. 30, 2021				295,885,508		18,393,186
Ending Balance at Sep. 30, 2021	$ 334.1			$ 3.0		$ (175.7)		$ 613.7		$ (100.3)			$ (6.6)