Debt (Narrative) (Details) - USD ($) $ in Millions			3 Months Ended			6 Months Ended	9 Months Ended
	Jun. 16, 2022	Oct. 12, 2020	Sep. 30, 2022	Sep. 30, 2022	Sep. 24, 2021	Jun. 16, 2022	Sep. 24, 2021	Dec. 31, 2021
Debt Instrument
Debtor Reorganization Items, Write-off of Debt Issuance Costs and Debt Discounts			$ 0.0	$ 0.0	$ 6.8	$ 0.0	$ 23.1
Liabilities Subject to Compromise			0.0	0.0				$ (6,397.7)
prepayment premium	1.00%					1.00%
Debt Instrument, Face Amount			3,583.6	3,583.6
Long-term Debt
Debt Instrument
Liabilities Subject to Compromise			0.0	0.0				$ (3,750.8)
2017 Revolving Credit Facility
Debt Instrument
Debt Instrument, Face Amount			0.0	0.0
10.00% First Lien Senior Notes
Debt Instrument
Debt Instrument, Face Amount	$ 495.0		495.0	495.0		$ 495.0
Term Loans due Sept 2024 and Feb 2025
Debt Instrument
Extinguishment of Debt, Amount	$ 1,762.6
10.00% Second Lien Senior Notes
Debt Instrument
Debt Instrument, Interest Rate, Stated Percentage	10.00%					10.00%
Debt Instrument, Face Amount	$ 322.9		321.9	321.9		$ 322.9
Debt Instrument, Redemption Price, Percentage	100.00%
Guaranteed Unsecured Notes
Debt Instrument
Extinguishment of Debt, Amount	$ 1,512.2
9.50% Debenture
Debt Instrument
Extinguishment of Debt, Amount	10.4
Debt Instrument, Face Amount			0.0	0.0
8.00% Debenture
Debt Instrument
Extinguishment of Debt, Amount	4.4
Debt Instrument, Face Amount			0.0	0.0
4.75% Senior Notes
Debt Instrument
Extinguishment of Debt, Amount	133.7
Debt Instrument, Face Amount			0.0	0.0
2017 Replacement Term Loan
Debt Instrument
Debt Instrument, Face Amount	$ 1,392.9		1,382.8	1,382.8		1,392.9
2017 Replacement Term Loan | London Interbank Offered Rate (LIBOR)
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate	5.25%
2017 Replacement Term Loan | Alternate Base Rate
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate	4.25%
2017 Replacement Term Loan | Minimum | London Interbank Offered Rate (LIBOR)
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate	0.75%
2017 Replacement Term Loan | Minimum | Alternate Base Rate
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate	1.75%
2018 Replacement Term Loan
Debt Instrument
Debt Instrument, Face Amount	$ 369.7		367.1	367.1		369.7
2018 Replacement Term Loan | London Interbank Offered Rate (LIBOR)
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate	5.50%
2018 Replacement Term Loan | Alternate Base Rate
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate	4.50%
2018 Replacement Term Loan | Minimum | London Interbank Offered Rate (LIBOR)
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate	0.75%
2018 Replacement Term Loan | Minimum | Alternate Base Rate
Debt Instrument
Debt Instrument, Basis Spread on Variable Rate	1.75%
Ten Point Zero Percent Second Lien Notes due 2029
Debt Instrument
Debt Instrument, Face Amount	$ 375.0		366.8	366.8		$ 375.0
Debt Instrument, Redemption Price, Percentage	100.00%
Eleven Point Five Percent First Lien Senior Secured Notes
Debt Instrument
Debt Instrument, Interest Rate, Stated Percentage	11.50%					11.50%
Debt Instrument, Face Amount			$ 650.0	$ 650.0
Debt Instrument, Redemption Price, Percentage	100.00%
Secured Debt
Debt Instrument
Debt Instrument, Interest Rate, Increase (Decrease)		200.00%
Term Loans due Sept 2024 and Feb 2025
Debt Instrument
Debt Instrument, Interest Rate, Increase (Decrease)		250.00%
Debentures | 9.50% Debenture
Debt Instrument
Debt Instrument, Interest Rate, Stated Percentage	9.50%					9.50%
Debentures | 9.50% Debenture | Level 2
Debt Instrument
Debt Instrument, Interest Rate, Stated Percentage	9.50%					9.50%
Debentures | 8.00% Debenture
Debt Instrument
Debt Instrument, Interest Rate, Stated Percentage	8.00%					8.00%
Debentures | 8.00% Debenture | Level 2
Debt Instrument
Debt Instrument, Interest Rate, Stated Percentage	8.00%					8.00%
Option A | 10.00% Second Lien Senior Notes
Debt Instrument
Debt Instrument, Repurchase Percentage	101.00%					101.00%
Option A | Ten Point Zero Percent Second Lien Notes due 2029
Debt Instrument
Debt Instrument, Repurchase Percentage	101.00%					101.00%
Option A | Eleven Point Five Percent First Lien Senior Secured Notes
Debt Instrument
Debt Instrument, Repurchase Percentage	101.00%					101.00%
Option B | 10.00% Second Lien Senior Notes
Debt Instrument
Debt Instrument, Repurchase Percentage	100.00%					100.00%
Option B | Ten Point Zero Percent Second Lien Notes due 2029
Debt Instrument
Debt Instrument, Repurchase Percentage	100.00%					100.00%
Option B | Eleven Point Five Percent First Lien Senior Secured Notes
Debt Instrument
Debt Instrument, Repurchase Percentage	100.00%					100.00%