Segment and Geographical Data (Schedule of Net Sales from External Costumers by Product) (Details) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016		Sep. 30, 2016	Jun. 24, 2016	Mar. 25, 2016	Dec. 25, 2015	Dec. 29, 2017	Sep. 30, 2016		Sep. 25, 2015
Segment Reporting Information [Line Items]
Net sales		$ 792.3	$ 793.9	$ 824.5	$ 810.9	$ 829.9		$ 887.2	$ 866.6	$ 815.8	$ 811.2	$ 3,221.6	$ 3,380.8		$ 2,923.1
Operating Segments
Segment Reporting Information [Line Items]
Net sales	[1]					816.0						3,164.8	3,325.8		2,874.4
Operating Segments | Specialty Generics [Member]
Segment Reporting Information [Line Items]
Net sales						212.9						839.5	1,025.2		1,251.6
Operating Segments | Specialty Brands [Member]
Segment Reporting Information [Line Items]
Net sales						603.1						2,325.3	2,300.6		1,622.8
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Net sales	[2]					13.9	[3]					56.8	55.0	[3]	48.7	[3]
Hydrocodone (API) and hydrocodone-containing tablets | Operating Segments | Specialty Generics [Member]
Segment Reporting Information [Line Items]
Net sales						22.0						71.7	103.5		136.5
Oxycodone (API) and oxycodone-containing tablets | Operating Segments | Specialty Generics [Member]
Segment Reporting Information [Line Items]
Net sales						24.3						78.8	126.2		154.6
Methylphenidate ER | Operating Segments | Specialty Generics [Member]
Segment Reporting Information [Line Items]
Net sales						23.2						85.3	146.5		167.2
Other controlled substances | Operating Segments | Specialty Generics [Member]
Segment Reporting Information [Line Items]
Net sales						104.9						409.6	468.1		572.2
Other | Operating Segments | Specialty Generics [Member]
Segment Reporting Information [Line Items]
Net sales						38.5						194.1	180.9		221.1
Hemostasis Products | Operating Segments | Specialty Brands [Member]
Segment Reporting Information [Line Items]
Net sales						13.4						55.1	42.5		0.0
Ofirmev | Operating Segments | Specialty Brands [Member]
Segment Reporting Information [Line Items]
Net sales						72.5						302.5	284.3		263.0
H.P. Acthar Gel | Operating Segments | Specialty Brands [Member]
Segment Reporting Information [Line Items]
Net sales						325.4						1,195.1	1,160.4		1,037.3
Therakos | Operating Segments | Specialty Brands [Member]
Segment Reporting Information [Line Items]
Net sales						47.4						214.9	207.6		0.0
Other | Operating Segments | Specialty Brands [Member]
Segment Reporting Information [Line Items]
Net sales						26.1						52.5	131.5		137.3
Product Concentration Risk | Net Sales Attributable to Products | Inomax
Segment Reporting Information [Line Items]
Net sales						$ 118.3						$ 505.2	$ 474.3		$ 185.2

[1] Amounts represent sales to external customers. There were no intersegment sales.

[2] Represents net sales from an ongoing, post-divestiture supply agreement with the acquirer of the CMDS business. Amounts for periods prior to the divestiture represent the reclassification of intercompany sales to third-party sales to conform with the expected presentation of the ongoing supply agreement.

[3] Represents net sales from an ongoing, post-divestiture supply agreement with the acquirer of the CMDS business. Amounts for periods prior to the divestiture represent the reclassification of intercompany sales to third-party sales to conform with the expected presentation of the ongoing supply agreement.