CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' DEFICIT - USD ($) $ in Millions		Common Stock	Treasury Stock at Cost	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Balances at beginning of period at Dec. 31, 2019		$ 0.9	$ (79.7)	$ 322.8	$ (15.5)	$ (474.4)	$ (245.9)
Balances at beginning of period (in shares) at Dec. 31, 2019		84,103,108
Increase (Decrease) in Stockholders' Deficit
Changes in accumulated other comprehensive gain (loss)					(3.0)		(3.0)
Stock-based compensation				2.7			2.7
Issuance of restricted stock, net (in shares)		2,858,421
Purchase of shares			(0.7)				(0.7)
Purchase of shares (in shares)		(199,520)
Net income (loss)						0.1	0.1
Balances at end of period at Mar. 31, 2020		$ 0.9	(80.4)	325.5	(18.5)	(474.3)	(246.8)
Balances at end of period (in shares) at Mar. 31, 2020		86,762,009
Balances at beginning of period at Dec. 31, 2019		$ 0.9	(79.7)	322.8	(15.5)	(474.4)	(245.9)
Balances at beginning of period (in shares) at Dec. 31, 2019		84,103,108
Increase (Decrease) in Stockholders' Deficit
Net income (loss)							11.3
Balances at end of period at Sep. 30, 2020		$ 0.9	(80.7)	331.1	(10.7)	(463.1)	(222.5)
Balances at end of period (in shares) at Sep. 30, 2020		86,856,478
Balances at beginning of period at Mar. 31, 2020		$ 0.9	(80.4)	325.5	(18.5)	(474.3)	(246.8)
Balances at beginning of period (in shares) at Mar. 31, 2020		86,762,009
Increase (Decrease) in Stockholders' Deficit
Changes in accumulated other comprehensive gain (loss)					3.3		3.3
Stock-based compensation				3.0			3.0
Issuance of restricted stock, net (in shares)		349,673
Purchase of shares			(0.3)				(0.3)
Purchase of shares (in shares)		(46,917)
Net income (loss)						2.2	2.2
Balances at end of period at Jun. 30, 2020	[1]	$ 0.9	(80.7)	328.5	(15.2)	(472.1)	(238.6)
Balances at end of period (in shares) at Jun. 30, 2020	[1]	87,064,765
Increase (Decrease) in Stockholders' Deficit
Changes in accumulated other comprehensive gain (loss)					4.5		4.5
Stock-based compensation				2.6			2.6
Issuance of restricted stock, net (in shares)		(198,182)
Purchase of shares (in shares)		(10,105)
Net income (loss)						9.0	9.0
Balances at end of period at Sep. 30, 2020		$ 0.9	(80.7)	331.1	(10.7)	(463.1)	(222.5)
Balances at end of period (in shares) at Sep. 30, 2020		86,856,478
Balances at beginning of period at Dec. 31, 2020		$ 1.0	(80.7)	333.8	(6.5)	(460.0)	$ (212.4)
Balances at beginning of period (in shares) at Dec. 31, 2020		86,847,797					86,847,797
Increase (Decrease) in Stockholders' Deficit
Changes in accumulated other comprehensive gain (loss)					4.3		$ 4.3
Stock-based compensation				3.1			3.1
Issuance of restricted stock, net (in shares)		666,127
Purchase of shares			(6.6)				(6.6)
Purchase of shares (in shares)		(397,186)
Net income (loss)						9.6	9.6
Balances at end of period at Mar. 31, 2021		$ 1.0	(87.3)	336.9	(2.2)	(450.4)	(202.0)
Balances at end of period (in shares) at Mar. 31, 2021		87,116,738
Balances at beginning of period at Dec. 31, 2020		$ 1.0	(80.7)	333.8	(6.5)	(460.0)	$ (212.4)
Balances at beginning of period (in shares) at Dec. 31, 2020		86,847,797					86,847,797
Increase (Decrease) in Stockholders' Deficit
Net income (loss)							$ 539.9
Balances at end of period at Sep. 30, 2021		$ 1.0	(88.7)	345.0		79.9	$ 337.2
Balances at end of period (in shares) at Sep. 30, 2021		87,191,153					87,191,153
Balances at beginning of period at Mar. 31, 2021		$ 1.0	(87.3)	336.9	(2.2)	(450.4)	$ (202.0)
Balances at beginning of period (in shares) at Mar. 31, 2021		87,116,738
Increase (Decrease) in Stockholders' Deficit
Changes in accumulated other comprehensive gain (loss)					$ 2.2		2.2
Stock-based compensation				4.0			4.0
Issuance of restricted stock, net (in shares)		34,929
Purchase of shares			(0.8)				(0.8)
Purchase of shares (in shares)		(40,473)
Net income (loss)						12.4	12.4
Balances at end of period at Jun. 30, 2021		$ 1.0	(88.1)	340.9		(438.0)	(184.2)
Balances at end of period (in shares) at Jun. 30, 2021		87,111,194
Increase (Decrease) in Stockholders' Deficit
Stock-based compensation				4.1			4.1
Issuance of restricted stock, net (in shares)		106,642
Purchase of shares			(0.6)				(0.6)
Purchase of shares (in shares)		(26,683)
Net income (loss)						517.9	517.9
Balances at end of period at Sep. 30, 2021		$ 1.0	$ (88.7)	$ 345.0		$ 79.9	$ 337.2
Balances at end of period (in shares) at Sep. 30, 2021		87,191,153					87,191,153

[1] Included in outstanding shares as of March 31, 2020, June, 30, 2020 and September 30, 2020 are 5,292,277, 5,322,864 and 5,072,695, respectively, of non-vested shares of restricted stock awards granted to employees and directors.