Consolidated Statements of Equity (Deficit) - USD ($) shares in Millions, $ in Millions	Total	Preferred Shares [Member]	Common Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance, Equity (Deficit) at Dec. 31, 2020	$ (191.1)	$ 129.4	$ 0.5	$ 2,670.3	$ (2,831.6)	$ (159.7)
Beginning Balance, Shares at Dec. 31, 2020		3.1
Beginning Balance, Shares at Dec. 31, 2020			50.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(81.3)				(81.3)
Other comprehensive income	37.5					37.5
Shares issued under employee plans	0.0		$ 0.0
Shares issued under employee plans, Shares			0.2
Shares purchased under employee plans and other	(2.0)			(2.0)
Stock-based compensation	4.3			4.3
Equity-based award modification	(10.2)			(10.2)
Dividends on preferred stock	(7.6)			(7.6)
Ending Balance, Equity (Deficit) at Sep. 07, 2021	(250.4)	$ 129.4	$ 0.5	2,654.8	(2,912.9)	(122.2)
Ending Balance, Shares at Sep. 07, 2021		3.1
Ending Balance, Shares at Sep. 07, 2021			50.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(27.2)
Other comprehensive income	1.2
Ending Balance, Equity (Deficit) at Dec. 31, 2021	1,690.1	$ 0.0	$ 0.0	1,716.1	(27.2)	1.2
Ending Balance, Shares at Dec. 31, 2021		0.0
Ending Balance, Shares at Dec. 31, 2021			0.0
Beginning Balance, Equity (Deficit) at Sep. 08, 2021	0.0	$ 0.0	$ 0.0	0.0	0.0	0.0
Beginning Balance, Shares at Sep. 08, 2021		0.0
Beginning Balance, Shares at Sep. 08, 2021			0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(27.2)				(27.2)
Other comprehensive income	1.2					1.2
Capital contributions by Red Fiber Parent LLC	1,716.1			1,716.1
Ending Balance, Equity (Deficit) at Dec. 31, 2021	1,690.1	$ 0.0	$ 0.0	1,716.1	(27.2)	1.2
Ending Balance, Shares at Dec. 31, 2021		0.0
Ending Balance, Shares at Dec. 31, 2021			0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(130.9)				(130.9)
Other comprehensive income	18.3					18.3
Ending Balance, Equity (Deficit) at Dec. 31, 2022	1,577.5	$ 0.0	$ 0.0	1,716.1	(158.1)	19.5
Ending Balance, Shares at Dec. 31, 2022		0.0
Ending Balance, Shares at Dec. 31, 2022			0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(192.7)				(192.7)
Other comprehensive income	8.7					8.7
Capital contributions by Red Fiber Parent LLC	400.0			400.0
Ending Balance, Equity (Deficit) at Dec. 31, 2023	$ 1,793.5	$ 0.0	$ 0.0	$ 2,116.1	$ (350.8)	$ 28.2
Ending Balance, Shares at Dec. 31, 2023		0.0
Ending Balance, Shares at Dec. 31, 2023			0.0