Debt (Narrative) (Details) - USD ($) $ in Millions			1 Months Ended	6 Months Ended		11 Months Ended	12 Months Ended
	Nov. 14, 2023	Jun. 16, 2022	Dec. 29, 2023	Dec. 30, 2022	Jun. 16, 2022	Nov. 14, 2023	Dec. 31, 2021
Debt Instrument [Line Items]
Debt instrument, face amount			$ 1,647.8	$ 3,534.1
Long-term Debt, Gross			1,758.8	3,048.5
Debt Issuance Costs, Net			2.9	20.8
Repayments of Debt			102.2	50.1	$ 904.6	$ 102.6	$ 137.5
Debtor Reorganization Items, Write-off of Debt Issuance Costs and Debt Discounts			0.0	0.0	0.0	21.2	23.1
Issuance of external debt		$ 650.0	0.0	0.0	650.0	380.0	0.0
Derivative Liability	$ 15.1					15.1
Debtor Reorganization Items, Gain (Loss) on Settlement of Other Claims, Net			0.0	0.0	5.4	1,139.5	$ (0.5)
Accretion of Debt Discount
Debt Instrument [Line Items]
Debtor Reorganization Items, Gain (Loss) on Settlement of Other Claims, Net						377.6
Ten Point Zero Percent First Lien Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		495.0	0.0	495.0	495.0
Ten Point Zero Percent First Lien Notes [Member] | Reorganization, Chapter 11, Plan Effect Adjustment
Debt Instrument [Line Items]
Debt instrument, face amount		495.0			495.0
Debt Issuance Costs, Gross		5.1			5.1
Term Loans due Sept 2024 and Feb 2025 [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	1,716.8
Ten Point Zero Percent Second Lien Notes (New 2L Notes)
Debt Instrument [Line Items]
Debt instrument, face amount			0.0	321.9
Extinguishment of Debt, Amount	321.9
2017 Replacement Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount		1,392.9	0.0	1,374.1	1,392.9
Debt Issuance Costs, Net			0.0	0.0
2017 Replacement Term Loan | Reorganization, Chapter 11, Plan Effect Adjustment
Debt Instrument [Line Items]
Debt instrument, face amount		1,392.9			1,392.9
2018 Replacement Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount		369.7	0.0	364.8	369.7
Debt Issuance Costs, Net			0.0	0.0
2018 Replacement Term Loan | Reorganization, Chapter 11, Plan Effect Adjustment
Debt Instrument [Line Items]
Debt instrument, face amount		369.7			369.7
Eleven Point Five Percent First Lien Senior Secured Notes
Debt Instrument [Line Items]
Debt instrument, face amount			0.0	650.0
Extinguishment of Debt, Amount	650.0
Debt Issuance Costs, Net			0.0	20.8
Debtor Reorganization Items, Write-off of Debt Issuance Costs and Debt Discounts						18.5
Eleven Point Five Percent First Lien Senior Secured Notes | Reorganization, Chapter 11, Plan Effect Adjustment
Debt Instrument [Line Items]
Issuance of external debt		650.0
Ten Point Zero Percent Second Lien Notes due 2029
Debt Instrument [Line Items]
Debt instrument, face amount			0.0	328.3
Extinguishment of Debt, Amount	328.3
Debt Issuance Costs, Net			0.0	0.0
Ten Point Zero Percent Second Lien Notes due 2029 | Reorganization, Chapter 11, Plan Effect Adjustment
Debt Instrument [Line Items]
Debt instrument, face amount		375.0			375.0
Receivables Financing Facility
Debt Instrument [Line Items]
Debt instrument, face amount		200.0	0.0	0.0	200.0
Debt Issuance Costs, Net			2.9	0.0
Debt Issuance Costs, Gross	1.7					1.7
Ten Point Zero Percent First Lien Notes Due April 2025
Debt Instrument [Line Items]
Debt instrument, face amount		$ 495.0			$ 495.0
Extinguishment of Debt, Amount	495.0
First-Out Takeback Term Loan Due November 2028
Debt Instrument [Line Items]
Debt instrument, face amount	$ 229.4		$ 228.8	0.0		$ 229.4
Long-term Debt, Weighted Average Interest Rate, at Point in Time			11.40%
Debt Issuance Costs, Net			$ 0.0	0.0
Debt Instrument, Stated Interest Rate, Amortization	1.00%					1.00%
Second-Out Takeback Term Loan Due November 2028
Debt Instrument [Line Items]
Debt instrument, face amount	$ 642.0		$ 640.4	0.0		$ 642.0
Long-term Debt, Weighted Average Interest Rate, at Point in Time			13.40%
Debt Issuance Costs, Net			$ 0.0	0.0
Debt Instrument, Stated Interest Rate, Amortization	1.00%					1.00%
Fourteen Point Seven Five Percent Second-Out Takeback Notes
Debt Instrument [Line Items]
Debt instrument, face amount	$ 778.6		778.6	0.0		$ 778.6
Stated interest rate	14.75%					14.75%
Debt Issuance Costs, Net			0.0	0.0
Takeback Term Loans
Debt Instrument [Line Items]
Debt instrument, face amount	$ 871.4					$ 871.4
Excess Cash Flow Threshold	$ 100.0					$ 100.0
Senior Notes | Five Point Six Two Five Percent Note
Debt Instrument [Line Items]
Stated interest rate		5.625%			5.625%
Senior Notes | Five Point Five Percent Notes [Member]
Debt Instrument [Line Items]
Stated interest rate		5.50%			5.50%
Senior Notes | Ten Point Zero Percent Second Lien Notes (New 2L Notes)
Debt Instrument [Line Items]
Stated interest rate		10.00%			10.00%
Secured Debt | Ten Point Zero Percent First Lien Notes [Member]
Debt Instrument [Line Items]
Debt Issuance Costs, Net			0.0	0.0
Secured Debt | Ten Point Zero Percent Second Lien Notes (New 2L Notes)
Debt Instrument [Line Items]
Debt Issuance Costs, Net			$ 0.0	$ 0.0
Alternate Base Rate | First-Out Takeback Term Loan Due November 2028
Debt Instrument [Line Items]
Variable interest rate	6.50%
Alternate Base Rate | Second-Out Takeback Term Loan Due November 2028
Debt Instrument [Line Items]
Variable interest rate	8.50%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | First-Out Takeback Term Loan Due November 2028
Debt Instrument [Line Items]
Variable interest rate	7.50%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | First-Out Takeback Term Loan Due November 2028 | Minimum
Debt Instrument [Line Items]
Variable interest rate		450.00%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Second-Out Takeback Term Loan Due November 2028
Debt Instrument [Line Items]
Variable interest rate	950.00%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Second-Out Takeback Term Loan Due November 2028 | Minimum
Debt Instrument [Line Items]
Variable interest rate		4.50%