Debt (Schedule of Long term debt) (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 25, 2020
Secured debt:
Long-term Debt, Current Maturities		$ (1,395.0)	$ (3,622.6)
Unsecured debt:
Long-term Debt, Gross		0.0	0.0
Debt Issuance Costs, Noncurrent, Net	[1]	0.0	0.0
Debt Issuance Costs, Net	[1]	6.1	34.7
Debt, Long-term and Short-term, Combined Amount		1,660.7	1,660.7
Debt, Long-term and Short-term, Combined Amount		5,145.8	5,283.3
Debt Issuance Costs, Current, Net	[1]	(6.1)	(34.7)
Secured Debt		3,485.1	3,622.6
Liabilities Subject to Compromise		(6,397.7)	(4,192.6)
Long-term Debt [Member]
Unsecured debt:
Liabilities Subject to Compromise	[2],[3]	(3,750.8)	(1,660.7)
Liabilities Subject to Compromise
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	0.0
8.00% debentures due March 2023
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount		4.4	4.4
4.75% senior notes due April 2023
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount		133.7	133.7
9.50% debentures due May 2022
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount		10.4	10.4
5.75% senior notes due August 2022
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount		610.3	610.3
Five Point Six Two Five Percent Note
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount		514.7	514.7
Five Point Five Percent Notes [Member]
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount		387.2	387.2
2017 Revolving Credit Facility
Unsecured debt:
Secured Debt		900.0	900.0
Term Loan due Sept 2024 [Member]
Unsecured debt:
Secured Debt		1,396.5	1,505.2
Term Loan due 2025 [Member]
Unsecured debt:
Secured Debt		370.7	399.5
Ten Point Zero Percent First Lien Notes [Member]
Unsecured debt:
Secured Debt		495.0	495.0
Ten Point Zero Percent Second Lien Notes [Member]
Unsecured debt:
Secured Debt		322.9	322.9
Senior Notes | 4.75% senior notes due April 2023
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount			133.7
Senior Notes | 5.75% senior notes due August 2022
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount		610.3	610.3
Debentures
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	0.0
Debentures | 8.00% debentures due March 2023
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	0.0
Debentures | 4.75% senior notes due April 2023
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	0.0
Debentures | 9.50% debentures due May 2022
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	0.0
Debentures | 5.75% senior notes due August 2022
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	0.0
Debentures | Five Point Six Two Five Percent Note
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	0.0
Debt, Long-term and Short-term, Combined Amount			514.7
Debentures | Five Point Five Percent Notes [Member]
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	0.0
Debt, Long-term and Short-term, Combined Amount			387.2
Debentures | 2017 Revolving Credit Facility
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount			900.0
Debentures | Ten Point Zero Percent First Lien Notes [Member]
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount			495.0
Debentures | Ten Point Zero Percent Second Lien Notes [Member]
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount			322.9
Secured Debt
Unsecured debt:
Debt Issuance Costs, Net	[1]	6.1	34.7
Secured Debt | 2017 Revolving Credit Facility
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.2	1.7
Secured Debt | Term Loan due Sept 2024 [Member]
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	12.3
Secured Debt			1,505.2
Secured Debt | Term Loan due 2025 [Member]
Unsecured debt:
Debt Issuance Costs, Net	[1]	0.0	5.0
Secured Debt			399.5
Secured Debt | Ten Point Zero Percent First Lien Notes [Member]
Unsecured debt:
Debt Issuance Costs, Net	[1]	5.9	7.7
Secured Debt | Ten Point Zero Percent Second Lien Notes [Member]
Unsecured debt:
Debt Issuance Costs, Net	[1]	$ 0.0	8.0
Debentures | 8.00% debentures due March 2023
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount			4.4
Debentures | 9.50% debentures due May 2022
Unsecured debt:
Debt, Long-term and Short-term, Combined Amount			$ 10.4

[1] As a result of the Company's Chapter 11 Cases, the Company expensed $23.1 million and $10.2 million of unamortized discount and debt issuance costs, net, recorded in reorganization items, net in the consolidated statements of operations for fiscal 2021 and 2020, respectively.

[2] In connection with the Company's Chapter 11 Cases, $3,750.8 million and $1,660.7 million of outstanding debt instruments have been classified as LSTC in the Company's consolidated balance sheets as of December 31, 2021 and December 25, 2020, respectively. Up to the Petition Date, the Company continued to accrue interest expense in relation to the unsecured debt instruments classified as LSTC. The Company continues to accrue and pay interest on the outstanding secured debt instruments classified as LSTC in conjunction with the cash collateral order. Refer to Note 2 for further information.

[3] Subsequent to December 25, 2020, in accordance with the agreement in principle reached with the Settling Second Lien Noteholders on September 2, 2021 and Joinder and Amendment to the RSA entered into in March 2021, $322.9 million of Second Lien Notes and $1,767.2 million of outstanding senior secured term loans, respectively, were classified as LSTC in the Company's consolidated balance sheet as of December 31, 2021.