Commitments and Contingencies (Narrative) (Details) $ / shares in Units, $ in Millions						3 Months Ended		9 Months Ended			12 Months Ended	103 Months Ended
	Sep. 02, 2021 USD ($)	Oct. 12, 2020 USD ($)	Oct. 11, 2020 USD ($)	Feb. 25, 2020 USD ($) $ / shares	Oct. 01, 2019 USD ($)	Sep. 24, 2021 USD ($)	Sep. 25, 2020 USD ($)	Sep. 24, 2021 USD ($) lawsuit	Sep. 25, 2020 USD ($)	[1]	Dec. 25, 2020 USD ($)	Aug. 01, 2019 USD ($)
Loss Contingencies [Line Items]
Medicaid lawsuit (Note 12)											$ 641.1
Settlement Warrants, Fair Value Disclosure						$ 0.0		$ 0.0			0.0
Liabilities subject to compromise (Note 2)						6,335.5		6,335.5			4,192.6
Interest Payable, Installment Sales						12.4		12.4			28.2
Decrease, Interest Payable, Installment Sales								15.8
Sales [Member]
Loss Contingencies [Line Items]
Medicaid lawsuit (Note 12)						0.0	$ (0.7)	0.0	$ (535.1)		536.0
Operating Expenses
Loss Contingencies [Line Items]
Medicaid lawsuit (Note 12)											105.1
Medicaid Lawsuit [Member]
Loss Contingencies [Line Items]
Liabilities subject to compromise (Note 2)						634.1		634.1			638.9
Acthar | Humana Inc. [Member]
Loss Contingencies [Line Items]
Proceeds from Customers												$ 700.0
Boston Civil Investigative Demand [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual						0.0		0.0
Medicaid Lawsuit [Member]
Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party, Post Closing Settlement Amount, Total		$ 260.0
Loss Contingency Accrual						0.0		$ 0.0
Restructuring Support Agreement, Proposed Debt, Term			7 years
Medicaid Lawsuit [Member] | Maximum
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss			$ 640.0
Track 1 Cases [Member]
Loss Contingencies [Line Items]
Payments for Legal Settlements					$ 24.0
Loss Contingency Accrual, Product Liability, Gross					6.0
Loss Contingency, Accrual, Noncurrent					$ 0.5
Opioid crisis [Member] | Cities, Counties, and/or Other Government-related Persons/Entities [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit								2,618
Opioid crisis [Member] | Hospitals, Health Systems, Unions, Health and Welfare Fund or Third-Party Payers [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit								270
Opioid crisis [Member] | Individuals [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit								124
Opioid crisis [Member] | Schools and School Boards [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit								6
Opioid crisis [Member] | State Attorney Generals [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs | lawsuit								17
Opioid Claimant Trust [Member]
Loss Contingencies [Line Items]
Warrant, Exercise Price | $ / shares				$ 3.15
Restructuring Support Agreement Proposed Settlement, Year Three through Seven			150.0
Restructuring Support Agreement, Proposed Debt, Term				8 years
Restructuring Support Agreement Proposed Settlement, Year Eight	$ 125.0
Opioid Claimant Trust [Member] | Restructuring Support Agreement [Member]
Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party, Settlement Closing Amount			450.0
Litigation Settlement, Amount Awarded to Other Party, Post Closing Settlement Amount, Year One & Two			200.0
Restructuring Support Agreement Proposed Settlement, Year Three through Seven			150.0
Restructuring Support Agreement Proposed Settlement, Year Eight	125.0
Opioid Claimant Trust [Member] | Maximum
Loss Contingencies [Line Items]
Loss Contingency Accrual				$ 1,600.0		$ 1,725.0		$ 1,725.0			$ 1,600.0
Opioid Claimant Trust [Member] | Maximum | Restructuring Support Agreement [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual	$ 1,725.0
Equity Value of Opioid Claimants' Ownership			$ 1,551.0
Senior Notes | 5.75% Senior Notes
Loss Contingencies [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						5.75%		5.75%
Senior Notes | 10.00% Second Lien Senior Notes
Loss Contingencies [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			10.00%
Other Ownership Interest [Member] | Opioid Claimant Trust [Member] | Maximum
Loss Contingencies [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners				19.99%
Other Ownership Interest [Member] | Opioid Claimant Trust [Member] | Maximum | Restructuring Support Agreement [Member]
Loss Contingencies [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners			19.99%

[1] 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 Pharmaceuticals Inc. ("Questcor") in August 2014. See Note 12 for further detail on the status of the Medicaid lawsuit.