Revenue from Contracts with Customers (Details) - USD ($) $ in Millions			3 Months Ended				6 Months Ended
		Jun. 26, 2020	Jun. 26, 2020		Jun. 14, 2020	Jun. 28, 2019	Jun. 26, 2020		Jun. 14, 2020	Jun. 28, 2019	Dec. 27, 2019	Dec. 28, 2018
Disaggregation of Revenue [Line Items]
Revenue Reserves		$ 832.7	$ 832.7			$ 374.4	$ 832.7			$ 374.4	$ 337.4	$ 405.4
Revenue Reserve Provision							990.0			1,260.7
Revenue Reserve Payments or Credits							(1,029.1)			(1,291.7)
Deferred Revenue, Revenue Recognized							3.6			9.2
Contract with Customer, Liability		3.8	3.8				3.8				6.2
Contract with Customer, Liability, Current		3.4	3.4				3.4				5.6
Capitalized Contract Cost, Gross		26.8	26.8				26.8				26.5
Capitalized Contract Cost, Amortization							2.7			3.4
Contract with Customer, Liability, Noncurrent		0.4	0.4				0.4				0.6
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)			166.5			823.3	832.3			1,613.9
Medicaid lawsuit (Note 11)			639.7
Medicaid Lawsuit [Member]
Disaggregation of Revenue [Line Items]
Decrease in revenue		8.6			$ 12.3				$ 27.6
Operating Expense [Member]
Disaggregation of Revenue [Line Items]
Medicaid lawsuit (Note 11)			105.3			0.0	105.3			0.0
Sales [Member]
Disaggregation of Revenue [Line Items]
Medicaid lawsuit (Note 11)			$ 534.4	[1],[2]		$ 0.0	$ 534.4	[1],[2]		$ 0.0
Sales Channel, Through Intermediary [Member] | Medicaid Lawsuit [Member]
Disaggregation of Revenue [Line Items]
Decrease in revenue		6.8
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue			77.70%			82.90%	78.10%			81.80%
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue			22.30%			17.10%	21.90%			18.20%
Royalty [Member]
Disaggregation of Revenue [Line Items]
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)			$ 16.3			$ 19.4	$ 31.9			$ 36.8
Rebates and Chargebacks [Member]
Disaggregation of Revenue [Line Items]
Revenue Reserves		795.7	795.7			328.4	795.7			328.4	295.8	354.3
Revenue Reserve Provision							947.5	[3]		1,214.3
Revenue Reserve Payments or Credits							(982.0)			(1,240.2)
Rebates and Chargebacks [Member] | Sales [Member]
Disaggregation of Revenue [Line Items]
Medicaid lawsuit (Note 11)	[4]						534.4
Allowance for Sales Returns [Member]
Disaggregation of Revenue [Line Items]
Revenue Reserves		26.3	26.3			30.1	26.3			30.1	28.4	34.0
Revenue Reserve Provision							13.3			11.7
Revenue Reserve Payments or Credits							(15.4)			(15.6)
Medicaid lawsuit (Note 11)							0.0
Other Sales Deductions [Member]
Disaggregation of Revenue [Line Items]
Revenue Reserves		$ 10.7	$ 10.7			$ 15.9	10.7			15.9	$ 13.2	$ 17.1
Revenue Reserve Provision							29.2			34.7
Revenue Reserve Payments or Credits							(31.7)			$ (35.9)
Medicaid lawsuit (Note 11)							$ 0.0
Minimum
Disaggregation of Revenue [Line Items]
Royalty Rate Percentage							18.00%
Maximum
Disaggregation of Revenue [Line Items]
Royalty Rate Percentage							26.00%

[1] Of this amount, $12.3 million and $27.6 million represent the impact of the Medicaid rebate calculation through June 14, 2020 for the three and six months ended June 26, 2020, respectively.

[2] Specialty Brands net sales for the three and six months ended June 26, 2020 includes the prospective change to the Medicaid rebate calculation, which served to reduce Acthar Gel net sales by $8.6 million for the period from June 15, 2020 through June 26, 2020, of which $6.8 million represents the channel impact. Of the $534.4 million recorded as a component of net sales, $12.3 million and $27.6 million represent the impact of the Medicaid rebate calculation through June 14, 2020 for the three and six months ended June 26, 2020, respectively. See Note 11 for further detail on the status of the Medicaid lawsuit.

[3] Rebates and Chargebacks include the prospective change to the Medicaid rebate calculation of $8.6 million for the period from June 15, 2020 to June 26, 2020, of which $6.8 million represents the channel impact. See Note 11 for further detail on the status of the Medicaid lawsuit.

[4] 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 11 for further detail on the status of the Medicaid lawsuit.