Segment Data (Schedule of Net Sales from External Customers by Products) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended			12 Months Ended
		Sep. 24, 2021	Sep. 25, 2020	Sep. 24, 2021	Sep. 25, 2020		Dec. 25, 2020
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		$ 507.2	$ 698.3	$ 1,611.6	$ 1,530.6
Medicaid lawsuit (Note 12)							$ (641.1)
Operating Segments
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		507.2	699.0	1,611.6	2,065.7
Sales [Member]
Segment Reporting Information
Medicaid lawsuit (Note 12)		0.0	0.7	0.0	535.1	[1]	$ (536.0)
Specialty Brands | Operating Segments
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		359.7	539.6	1,149.6	1,553.0
Specialty Generics | Operating Segments
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		147.5	159.4	462.0	512.7
Acthar | Specialty Brands
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		143.4	195.3	423.9	576.6
Inomax | Specialty Brands
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		98.4	141.9	338.3	438.5
Ofirmev | Specialty Brands
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		4.7	88.7	24.0	216.0
Therakos immunotherapy | Specialty Brands
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		62.5	62.6	197.8	174.1
Amitiza [Member] | Specialty Brands
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)	[2]	49.6	47.7	155.8	138.2
Other | Specialty Brands
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		1.1	3.4	9.8	9.6
Other | Specialty Generics
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		5.0	6.0	17.1	14.5
Hydrocodone (API) [Member] | Specialty Generics
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		16.9	20.0	60.7	71.9
Oxycodone (API) [Member] | Specialty Generics
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		15.2	16.1	49.5	48.0
Acetaminophen (API) [Member] | Specialty Generics
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		49.6	54.9	146.8	154.5
Other Controlled Substances [Member] | Specialty Generics
Segment Reporting Information
Net sales (includes refined estimate of the retrospective one-time charge of $0.7 million and $535.1 million related to the Medicaid lawsuit for the three and nine months ended September 25, 2020)		$ 60.8	$ 62.4	$ 187.9	$ 223.8

[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.

[2] Amitiza consists of both product net sales and royalties. Refer to Note 2 for further details on Amitiza's revenues.