Debt (Details) - USD ($) $ in Millions		Sep. 24, 2021		Dec. 25, 2020
Current maturities of long-term debt
Debt Issuance Costs, Current, Net		$ 6.9		$ 34.7
Long-term Debt, Current Maturities		1,395.0		3,622.6
Long-term debt
Long-term Debt		0.0		0.0
Debt Issuance Costs		0.0		0.0
Total Debt Issuance Costs		6.9		34.7
Secured Debt		3,494.4		3,622.6
Unsecured Debt		1,660.7		1,660.7
Total Debt		5,155.1		5,283.3
Liabilities Subject to Compromise		(6,335.5)		(4,192.6)
Long-term Debt
Long-term debt
Liabilities Subject to Compromise	[1],[2]	(3,760.1)		(1,660.7)
Liabilities Subject to Compromise
Long-term debt
Total Debt Issuance Costs	[1]	0.0		0.0
Unsecured Debt
Long-term debt
Total Debt Issuance Costs		0.0		0.0
Secured Debt
Long-term debt
Total Debt Issuance Costs		6.9		34.7
Term Loan due 2025
Long-term debt
Secured Debt		372.6	[3]	399.5
Term Loan due 2025 | Secured Debt
Long-term debt
Total Debt Issuance Costs		0.0	[4]	5.0
Term Loan due 2024
Long-term debt
Secured Debt		1,403.9		1,505.2
Term Loan due 2024 | Secured Debt
Long-term debt
Total Debt Issuance Costs		0.0	[4]	12.3
9.50% Debenture
Long-term debt
Unsecured Debt		10.4		10.4
9.50% Debenture | Unsecured Debt
Long-term debt
Total Debt Issuance Costs		0.0		0.0
5.75% Senior Notes
Long-term debt
Unsecured Debt		610.3		610.3
5.75% Senior Notes | Unsecured Debt
Long-term debt
Total Debt Issuance Costs		0.0		0.0
8.00% Debenture
Long-term debt
Unsecured Debt		4.4		4.4
8.00% Debenture | Unsecured Debt
Long-term debt
Total Debt Issuance Costs		0.0		0.0
4.75% Senior Notes
Long-term debt
Unsecured Debt		133.7		133.7
4.75% Senior Notes | Unsecured Debt
Long-term debt
Total Debt Issuance Costs		0.0		0.0
5.625% Senior Notes
Long-term debt
Unsecured Debt		514.7		514.7
5.625% Senior Notes | Unsecured Debt
Long-term debt
Total Debt Issuance Costs		0.0		0.0
5.50% Senior Notes
Long-term debt
Unsecured Debt		387.2		387.2
5.50% Senior Notes | Unsecured Debt
Long-term debt
Total Debt Issuance Costs		0.0		0.0
10.00% Second Lien Senior Notes
Long-term debt
Secured Debt		322.9		322.9
10.00% Second Lien Senior Notes | Secured Debt
Long-term debt
Total Debt Issuance Costs		0.0	[4]	8.0
10.00% First Lien Senior Notes
Long-term debt
Secured Debt		495.0		495.0
10.00% First Lien Senior Notes | Secured Debt
Long-term debt
Total Debt Issuance Costs		6.3		7.7
2017 Revolving Credit Facility
Long-term debt
Secured Debt		900.0	[5]	900.0
2017 Revolving Credit Facility | Secured Debt
Long-term debt
Total Debt Issuance Costs		$ 0.6		$ 1.7

[1] In connection with the Company’s Chapter 11 Cases, $3,760.1 million and $1,660.7 million outstanding secured and unsecured debt instruments have been reclassified to LSTC in the Company's unaudited condensed consolidated balance sheets as of September 24, 2021 and December 25, 2020, respectively. Up to the date of reclassification to LSTC, the Company continued to accrue interest expense in relation to the unsecured debt instruments reclassified to 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

[2] 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 $1,776.5 million of outstanding senior secured term loans, respectively, were classified as LSTC in the Company's unaudited condensed consolidated balance sheet as of September 24, 2021.

[3] The applicable interest rate for the senior secured term loans includes the incremental 250 basis points as a result of the amendment to the cash collateral order that took effect on March 22, 2021. Refer to Note 2 for further discussion on the amendment.

[4] As a result of the Company's Chapter 11 Cases, the Company expensed $23.1 million of unamortized discount and debt issuance costs, net, recorded in reorganization items, net in the unaudited condensed consolidated statement of operations during the nine months ended September 24, 2021.

[5] Includes the incremental 200 basis points related to the cash adequate protection payments. Refer to Note 2 for further information.