Commitments and Contingencies (Narrative) (Details)											3 Months Ended	12 Months Ended
		Sep. 02, 2021 USD ($)	Oct. 12, 2020 USD ($)	Oct. 11, 2020 USD ($)	Feb. 25, 2020 USD ($) $ / shares	Feb. 01, 2020 USD ($)	Oct. 01, 2019 USD ($)	Aug. 08, 2019 USD ($)	Jun. 30, 2018 Defendent	May 01, 2007 Defendent	Sep. 27, 2019 USD ($)	Dec. 31, 2021 USD ($) lawsuit Case	Dec. 25, 2020 USD ($) Defendent		Dec. 27, 2019 USD ($) Defendent	Sep. 28, 2021 USD ($)	Apr. 21, 2020 USD ($)	Aug. 07, 2018 USD ($)	Jun. 29, 2018 USD ($)	Apr. 11, 2014 USD ($)
Loss Contingencies [Line Items]
Environmental liabilities												$ 95,800,000
Interest Payable, Installment Sales												12,400,000	$ 28,200,000
Decrease, Interest Payable, Installment Sales												15,800,000
Settlement Warrants, Fair Value Disclosure												0
Medicaid lawsuit charge													(641,100,000)
Liabilities subject to compromise (Note 2)												6,397,700,000	4,192,600,000
Environmental liabilities												43,000,000	59,800,000
Sales [Member]
Loss Contingencies [Line Items]
Medicaid lawsuit charge	[1]											0	536,000,000.0	[2]	$ 0
Operating Expenses
Loss Contingencies [Line Items]
Medicaid lawsuit charge													(105,100,000)
Track 1 Cases [Member]
Loss Contingencies [Line Items]
Payments for Legal Settlements							$ 24,000,000
Loss Contingency Accrual, Product Liability, Gross							6,000,000
Loss Contingency, Accrual, Noncurrent							$ 500,000
Occidental, Lower Passaic River [Member]
Loss Contingencies [Line Items]
Number of defendants | Defendent									120
Lower Passaic River, New Jersey
Loss Contingencies [Line Items]
Environmental liabilities												$ 26,100,000
Remedial cost, estimate																			$ 1,380,000,000	$ 1,700,000,000
Loss Contingency, Settlement Agreement, Amount																		$ 280,600
Asbestos Matters
Loss Contingencies [Line Items]
Pending claims | Case												11,800
Estimation of liability, historical term												4 years
Estimation of liability, expected future term of claims												7 years
Questcor Subpoena [Member]
Loss Contingencies [Line Items]
Payments for Legal Settlements											$ 15,400,000
Marietta, GA Litigation [Member]
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value						$ 2,000,000
Crab Orchard National Wildlife Refuge Superfund Site
Loss Contingencies [Line Items]
Environmental liabilities												$ 46,300,000
Environmental Remediation Expense												34,300,000
Upper 9 Miles, Lower Passaic River, New Jersey
Loss Contingencies [Line Items]
Remedial cost, estimate																$ 441,000,000
Other current liabilities
Loss Contingencies [Line Items]
Environmental liabilities, current												800,000
Medicaid Lawsuit [Member]
Loss Contingencies [Line Items]
Liabilities subject to compromise (Note 2)												634,700,000	638,900,000
Accrued Environmental Loss Contingencies
Loss Contingencies [Line Items]
Liabilities subject to compromise (Note 2)	[3]											52,000,000	$ 0
Accrued Environmental Loss Contingencies | Lower Passaic River, New Jersey
Loss Contingencies [Line Items]
Liabilities subject to compromise (Note 2)												4,600,000
U.S. House Committee Investigation [Member]
Loss Contingencies [Line Items]
Number of defendants | Defendent															11
Lower Passaic River, New Jersey
Loss Contingencies [Line Items]
Number of defendants | Defendent										70
National Benefit Fund Litigation [Member]
Loss Contingencies [Line Items]
Number of defendants | Defendent															30
Cesar Castillo, Inc., Litigation [Member]
Loss Contingencies [Line Items]
Number of defendants | Defendent													30
Opioid Claimant Trust [Member]
Loss Contingencies [Line Items]
Warrant, Exercise Price | $ / shares					$ 3.15
Litigation Settlement, Amount Awarded to Other Party, Post Closing Settlement Amount, Year Three through Seven				$ 150,000,000
Restructuring Support Agreement Proposed Settlement, Year Eight		$ 125,000,000
Opioid Claimant Trust [Member] | Restructuring Support Agreement [Member]
Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party, Settlement Closing Amount				450,000,000
Litigation Settlement, Amount Awarded to Other Party, Post Closing Settlement Amount, Year One & Two				200,000,000
Litigation Settlement, Amount Awarded to Other Party, Post Closing Settlement Amount, Year Three through Seven				150,000,000
Restructuring Support Agreement Proposed Settlement, Year Eight		$ 125,000,000
New York State Department of Financial Services [Member]
Loss Contingencies [Line Items]
Remedial cost, estimate																	$ 5,000
Medicaid Lawsuit [Member]
Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party, Post Closing Settlement Amount, Total			$ 260,000,000
Minimum
Loss Contingencies [Line Items]
Remedial cost, estimate												72,300,000
Minimum | Lower Passaic River, New Jersey
Loss Contingencies [Line Items]
Remedial cost, estimate																				365,000,000
Maximum
Loss Contingencies [Line Items]
Remedial cost, estimate												120,900,000
Maximum | Lower Passaic River, New Jersey
Loss Contingencies [Line Items]
Remedial cost, estimate																				$ 3,200,000,000
Maximum | Opioid Claimant Trust [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual					$ 1,600,000,000							1,725,000,000	$ 1,600,000,000
Maximum | Opioid Claimant Trust [Member] | Restructuring Support Agreement [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual				1,725,000,000
Equity Value of Opioid Claimants' Ownership				$ 1,551,000,000
Maximum | Opioid Claimant Trust [Member] | Ownership Interest [Member]
Loss Contingencies [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					19.99%
Maximum | Opioid Claimant Trust [Member] | Ownership Interest [Member] | Restructuring Support Agreement [Member]
Loss Contingencies [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners				19.99%
Maximum | Medicaid Lawsuit [Member]
Loss Contingencies [Line Items]
Remedial cost, estimate				$ 640,000,000
Maximum | Boston Civil Investigative Demand [Member]
Loss Contingencies [Line Items]
Remedial cost, estimate												1,280,000,000
Acthar Gel (1) | Humana Inc. [Member]
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value								$ 700,000,000
Fair Value, Measurements, Recurring
Loss Contingencies [Line Items]
Contingent consideration												27,300,000	34,700,000
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Loss Contingencies [Line Items]
Contingent consideration												27,300,000	34,700,000
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Stratatech [Member]
Loss Contingencies [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability												27,300,000	19,100,000
Fair Value, Measurements, Recurring | MNK-6105 [Member] | Fair Value, Inputs, Level 3 | Ocera [Member]
Loss Contingencies [Line Items]
Contingent consideration												$ 0	$ 15,600,000
Cities, Counties, and/or Other Government-related Persons/Entities [Member] | opioid crisis [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit												2,619
Hospitals, Health Systems, Unions, Health and Welfare Fund or Third-Party Payers [Member] | opioid crisis [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit												270
Individuals [Member] | opioid crisis [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit												124
Schools and School Boards [Member] | opioid crisis [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit												8
State Attorney Generals [Member] | opioid crisis [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit												17

[1] Specialty Brands net sales for fiscal 2020 includes the prospective change to the Medicaid rebate calculation, which served to reduce Acthar Gel net sales by $40.4 million for the period from June 15, 2020 through December 25, 2020. See Note 19 for further detail on the status of the Medicaid lawsuit.

[2] Excludes the $105.1 million that is reflected as a component of operating expenses as it represents a pre-acquisition contingency related to the portion of the liability that arose from sales of Acthar Gel prior to the Company's acquisition of Questcor in August 2014. See Note 19 for further detail on the status of the Medicaid lawsuit.

[3] Represents certain environmental liabilities intended to be discharged upon effectiveness of the plan of reorganization.