Segment Data (Schedule of Segment Reporting Information by Business Segment) (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended			12 Months Ended
		Jun. 25, 2021	Jun. 26, 2020		Jun. 25, 2021	Jun. 26, 2020		Dec. 25, 2020
Net sales (includes retrospective one-time charge of $534.4 million related to the Medicaid lawsuit for the three and six months ended June 26, 2020)		$ 546.4	$ 166.5		$ 1,104.4	$ 832.3
Operating Income (Loss)		10.9	(725.5)		(6.6)	(731.8)
Medicaid lawsuit (Note 12)								$ 641.1
Depreciation and amortization		(145.2)	(191.6)		(290.5)	(389.2)
Employee Benefits and Share-based Compensation		(2.4)	(6.6)		(6.0)	(13.3)
Restructuring and related charges, net		(6.7)	(14.4)		(7.8)	(12.6)
Opioid-related litigation settlement loss (gain) (Note 12)		0.0	8.5		0.0	(8.3)
Non-restructuring impairment charges		0.0	(63.5)		(64.5)	(63.5)
Sales [Member]
Medicaid lawsuit (Note 12)		0.0	(534.4)		0.0	(534.4)	[1]	$ 536.0
Specialty Brands
Restructuring and related charges, net		0.0	(0.1)		0.0	(0.1)
Specialty Generics
Restructuring and related charges, net		0.0	0.0		0.0	(0.1)
Corporate, Non-Segment
R&D Upfront Payment		0.0	(5.0)	[2]	0.0	(5.0)	[2]
Medicaid lawsuit (Note 12)		0.0	(639.7)		0.0	(639.7)
Corporate and unallocated expenses	[3]	(25.7)	(52.7)		(48.3)	(110.2)
Depreciation and amortization		(168.1)	(216.3)		(337.7)	(439.4)
Restructuring and related charges, net		(6.1)	(14.4)		(6.5)	(12.6)
Separation Costs	[4]	(0.3)	(20.7)		(0.9)	(42.0)
Opioid-related litigation settlement loss (gain) (Note 12)	[5]	0.0	(8.5)		0.0	8.3
Operating Segments
Net sales (includes retrospective one-time charge of $534.4 million related to the Medicaid lawsuit for the three and six months ended June 26, 2020)		546.4	700.9		1,104.4	1,366.7
Operating Income (Loss)		213.5	301.9		457.3	585.6
Operating Segments | Specialty Brands
Net sales (includes retrospective one-time charge of $534.4 million related to the Medicaid lawsuit for the three and six months ended June 26, 2020)		381.5	522.8		789.9	1,013.4
Operating Income (Loss)		186.6	252.7		398.7	473.2
Operating Segments | Specialty Generics
Net sales (includes retrospective one-time charge of $534.4 million related to the Medicaid lawsuit for the three and six months ended June 26, 2020)		164.9	178.1		314.5	353.3
Operating Income (Loss)		$ 26.9	$ 49.2		$ 58.6	$ 112.4

[1] Excludes the $105.3 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] Represents R&D expense incurred related to an upfront payment made to acquire product rights in Japan for terlipressin.

[3] Includes administration expenses and certain compensation, legal, environmental and other costs not charged to the Company's reportable segments.

[4] Represents costs included in SG&A expenses, primarily related to professional fees and costs incurred in preparation for the Chapter 11 proceedings. As of the Petition Date, professional fees directly related to the Chapter 11 proceedings that were previously reflected as separation costs are being classified on a go-forward basis as reorganization items, net.

[5] Represents the change in the Settlement Warrants' fair value. Refer to Note 12 for further information.