Consolidated Statements of Shareholders' Deficit - USD ($) $ in Millions	Total	Common Stock	Capital Surplus	Accumulated Deficit	Accumulated Other Comprehensive Loss	Treasury Stock, At Cost
Beginning balance at Dec. 31, 2019	$ (441.2)	$ 0.3	$ 2,332.9	$ (2,312.4)	$ (369.3)	$ (92.7)
Equity-based compensation	4.2		4.2
Equity issuance - UST commitment fee	46.7	0.2	46.5
Net income (loss)	(53.5)			(53.5)
Amortization of prior net losses	12.7				12.7
Amortization of prior net service credit	(0.4)				(0.4)
Settlement adjustment	2.7				2.7
Net actuarial gains (losses)	204.6				204.6
Foreign currency translation, net of tax	0.9				0.9
Ending balance at Dec. 31, 2020	(223.3)	0.5	2,383.6	(2,365.9)	(148.8)	(92.7)
Equity-based compensation	4.7		4.7
Net income (loss)	(109.1)			(109.1)
Amortization of prior net losses	12.1				12.1
Amortization of prior net service credit	(0.4)				(0.4)
Settlement adjustment	64.7				64.7
Net actuarial gains (losses)	(112.7)				(112.7)
Foreign currency translation, net of tax	0.5				0.5
Ending balance at Dec. 31, 2021	(363.5)	0.5	2,388.3	(2,475.0)	(184.6)	(92.7)
Equity-based compensation	5.1		5.1
Net income (loss)	21.8			21.8
Amortization of prior net losses	8.6				8.6
Amortization of prior net service credit	(0.4)				(0.4)
Settlement adjustment	12.1				12.1
Net actuarial gains (losses)	(62.4)				(62.4)
Foreign currency translation, net of tax	(2.8)				(2.8)
Ending balance at Dec. 31, 2022	$ (381.5)	$ 0.5	$ 2,393.4	$ (2,453.2)	$ (229.5)	$ (92.7)