Acquisitions and License Agreements (Narrative) (Details) - USD ($)						3 Months Ended								12 Months Ended
		Feb. 13, 2018	Dec. 11, 2017		Sep. 25, 2017	Dec. 27, 2019	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 27, 2019	Dec. 28, 2018	Dec. 29, 2017	Aug. 31, 2014
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired														$ 0	$ 699,900,000	$ 76,300,000
Long-term Debt, Gross						$ 4,788,300,000				$ 6,134,000,000.0				4,788,300,000	6,134,000,000.0
Net sales						804,900,000	$ 743,700,000	$ 823,300,000	$ 790,600,000	834,900,000	$ 799,900,000	$ 825,500,000	$ 755,300,000	3,162,500,000	3,215,600,000	3,221,600,000
Non-cash impairment charges														388,000,000.0	3,893,100,000	63,700,000
Operating Income (Loss)														(1,822,200,000)	(3,720,900,000)	492,900,000
Intangible asset amortization														853,400,000	740,200,000	694,500,000
Noninterest Income, Other Operating Income														39,000,000.0	15,500,000
Sucampo [Member]
Business Acquisition [Line Items]
Contingent consideration		$ 0
Total consideration		847,600,000
Cash used to acquire business		1,200,000,000
Total Debt		366,300,000
Net sales														217,200,000	190,500,000
Operating Income (Loss)														(210,600,000)	369,100,000
Intangible asset amortization														70,900,000	62,900,000
Silence Therapeutics [Member]
Business Acquisition [Line Items]
R&D upfront payment														20,000,000.0
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low						10,000,000.0								10,000,000.0
Contingent consideration, potential maximum						563,000,000.0								563,000,000.0
Ocera [Member]
Business Acquisition [Line Items]
Contingent consideration	[1]		$ 22,000,000.0
Business Combination, Consideration Transferred, Other			42,400,000
Total consideration			64,400,000	[1]											1,900,000	40,500,000
Cash used to acquire business													$ 1,900,000
Total Debt	[2]		0
Contingent consideration, potential maximum			$ 75,000,000.0
InfaCare [Member]
Business Acquisition [Line Items]
Contingent consideration	[3]				$ 35,000,000.0
Business Combination, Consideration Transferred, Other					80,400,000
Total consideration					73,100,000
Total Debt	[3]				30,000,000.0
Contingent consideration, potential maximum					345,000,000.0
Business Combination, Cash Paid for Consideration					37,200,000
Other liabilities (non-current)					$ 43,200,000
Mesoblast [Member]
Business Acquisition [Line Items]
Payments to Acquire Marketable Securities																21,500,000
Proceeds from Sale of Available-for-sale Securities, Equity															25,500,000
Marketable Securities, Realized Gain (Loss)															3,400,000
Questcor Pharmaceuticals, Inc.
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability						24,500,000				76,200,000				24,500,000	76,200,000		$ 195,400,000
Bristol-Myers Squibb | Licensing Agreements
Business Acquisition [Line Items]
Royalties paid														69,800,000	76,900,000	53,900,000
Milestone Payments															15,000,000.0
Term Loan due 2025 [Member] | Secured Debt
Business Acquisition [Line Items]
Loans Payable						403,600,000				597,000,000.0				403,600,000	597,000,000.0
Long-term Debt, Gross						$ 399,500,000				591,000,000.0				399,500,000	591,000,000.0
Term Loan due 2025 [Member] | Secured Debt | Sucampo [Member]
Business Acquisition [Line Items]
Loans Payable		600,000,000.0
2017 Revolving Credit Facility | Debentures
Business Acquisition [Line Items]
Long-term Debt, Gross		900,000,000.0								$ 220,000,000.0					220,000,000.0
Sucampo 2021 Notes [Member] | Convertible Debt Securities [Member]
Business Acquisition [Line Items]
Long-term Debt, Gross		$ 300,000,000.0
Stated interest rate		3.25%
Debt instrument, face amount		$ 1,000
Debt Conversion, Converted Instrument, Amount		$ 1,221
Cost of Sales
Business Acquisition [Line Items]
Amortization Of Inventory Step-Up To Cost Of Sales														10,000,000.0	120,800,000	$ 10,100,000
Cost of Sales | Sucampo [Member]
Business Acquisition [Line Items]
Amortization Of Inventory Step-Up To Cost Of Sales														$ 10,000,000.0	$ 118,800,000

[1] $1.9 million of the total consideration, net of cash was paid in fiscal 2018, subsequent to the Company's December 11, 2017 acquisition date.

[2] Of the $42.4 million net assets acquired for Ocera, $40.5 million and $1.9 million was paid in fiscal 2017 and 2018, respectively.

[3] During fiscal 2019, the Company recognized a full impairment of the IPR&D asset related to stannsoporfin of $113.5 million. During fiscal 2018, the Company reduced the contingent consideration liability related to this acquisition to zero through the recognition of a $35.0 million fair value adjustment. Refer to Note 13 and 21 for further information.