Condensed Consolidated Statements of Shareowners' Equity (Deficit) - USD ($) shares in Millions, $ in Millions	Total	Cumulative Convertible Preferred Shares [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance, Shareowners' Equity (Deficit) at Dec. 31, 2019	$ (140.0)	$ 129.4	$ 0.5	$ 2,676.2	$ (2,776.0)	$ (170.1)
Beginning Balance, Shares at Dec. 31, 2019		3.1
Beginning Balance, Shares at Dec. 31, 2019			50.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(50.0)				(50.0)
Other comprehensive income (loss)	(9.8)					(9.8)
Stock-based compensation	4.2			4.2
Dividends on preferred stock	(7.8)			(7.8)
Shares issued under employee plans			$ 0.0	0.0
Shares issued under employee plans, Shares			0.3
Shares purchased under employee plans and other	(1.1)			(1.1)
Ending Balance, Shareowners' Equity (Deficit) at Sep. 30, 2020	(204.5)	$ 129.4	$ 0.5	2,671.5	(2,826.0)	(179.9)
Ending Balance, Shares at Sep. 30, 2020		3.1
Ending Balance, Shares at Sep. 30, 2020			50.7
Beginning Balance, Shareowners' Equity (Deficit) at Jun. 30, 2020	(204.6)	$ 129.4	$ 0.5	2,672.9	(2,817.8)	(189.6)
Beginning Balance, Shares at Jun. 30, 2020		3.1
Beginning Balance, Shares at Jun. 30, 2020			50.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(8.2)				(8.2)
Other comprehensive income (loss)	9.7					9.7
Stock-based compensation	1.2			1.2
Dividends on preferred stock	(2.6)			(2.6)
Ending Balance, Shareowners' Equity (Deficit) at Sep. 30, 2020	(204.5)	$ 129.4	$ 0.5	2,671.5	(2,826.0)	(179.9)
Ending Balance, Shares at Sep. 30, 2020		3.1
Ending Balance, Shares at Sep. 30, 2020			50.7
Beginning Balance, Shareowners' 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 (loss)	37.5					37.5
Stock-based compensation	4.3			4.3
Dividends on preferred stock	(7.6)			(7.6)
Equity-based award modification	(10.2)			(10.2)
Shares issued under employee plans, Shares			0.2
Shares purchased under employee plans and other	(2.0)			(2.0)
Ending Balance, Shareowners' 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
Beginning Balance, Shareowners' Equity (Deficit) at Jun. 30, 2021	(183.2)	$ 129.4	$ 0.5	2,665.3	(2,839.2)	(139.2)
Beginning Balance, Shares at Jun. 30, 2021		3.1
Beginning Balance, Shares at Jun. 30, 2021			50.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(73.7)				(73.7)
Other comprehensive income (loss)	17.0					17.0
Stock-based compensation	2.1			2.1
Dividends on preferred stock	(2.4)			(2.4)
Equity-based award modification	(10.2)			(10.2)
Ending Balance, Shareowners' 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	(5.0)
Other comprehensive income (loss)	(1.2)
Ending Balance, Shareowners' Equity (Deficit) at Sep. 30, 2021	1,709.9			1,716.1	(5.0)	(1.2)
Ending Balance, Shares at Sep. 30, 2021			0.5
Beginning Balance, Shareowners' 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	(5.0)				(5.0)
Other comprehensive income (loss)	(1.2)					(1.2)
Capital contributions by Red Fiber Parent LLC	1,716.1			1,716.1
Capital contributions by Red Fiber Parent LLC, Shares			0.5
Ending Balance, Shareowners' Equity (Deficit) at Sep. 30, 2021	$ 1,709.9			$ 1,716.1	$ (5.0)	$ (1.2)
Ending Balance, Shares at Sep. 30, 2021			0.5