Segment Data - Schedule of Segment Reporting Information by Business Segment (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Aug. 01, 2025	Sep. 26, 2025	Sep. 27, 2024	Sep. 26, 2025	Sep. 27, 2024
Segment Reporting Information
Net sales		$ 753.1	$ 505.5	$ 1,658.1	$ 1,487.6
Cost of sales		499.1	284.4	969.4	907.5
Selling, general and administrative expenses		351.7	141.2	649.8	406.0
Research and development expenses		44.3	28.2	88.4	85.3
Restructuring charges, net		0.0	0.1	(2.2)	10.5
Operating (loss) income		(269.1)	36.4	(221.1)	46.1
Interest expense		70.6	59.0	136.0
Combination, integration, and other related expenses			0.0	136.9	0.0
Liabilities management and separation costs		33.3	15.2	36.9	32.2
Interest expense					(177.5)
Interest income		6.5	7.4	18.2	20.2
Gain on debt extinguishment	$ 4.6	4.6	0.0	4.6	0.0
Gain on divestiture		0.8	0.0	(5.9)	0.0
Other income (expense), net		0.8	(3.8)	2.2	(3.6)
Loss from continuing operations before income taxes		(327.0)	(19.0)	(338.0)	(114.8)
Depreciation and amortization				107.2	93.5
Specialty Brands
Segment Reporting Information
Net sales					817.8
Depreciation and amortization		42.9	16.3	67.2	60.2
Generics
Segment Reporting Information
Net sales					669.8
Depreciation and amortization		17.5	9.8	37.1	32.5
Sterile Injectables
Segment Reporting Information
Net sales					0.0
Depreciation and amortization		2.2	0.0	2.2	0.0
Operating Segments
Segment Reporting Information
Net sales		753.1	505.5	1,658.1
Cost of sales		494.1	280.8	956.8	896.6
Selling, general and administrative expenses		152.9	87.0	329.5	251.4
Research and development expenses		31.0	17.9	57.4	55.6
Restructuring charges, net			0.1	(2.2)	10.5
Operating (loss) income		75.1	119.7	316.6	273.5
Operating Segments | Specialty Brands
Segment Reporting Information
Net sales		416.0	286.0	887.6	817.8
Cost of sales		238.3	133.8	440.1	428.2
Selling, general and administrative expenses		115.4	63.7	233.8	189.1
Research and development expenses		16.1	10.7	31.7	36.2
Restructuring charges, net			0.1	(2.2)	10.5
Operating (loss) income		46.2	77.7	184.2	153.8
Operating Segments | Generics
Segment Reporting Information
Net sales		289.9	219.5	723.3	669.8
Cost of sales		198.9	147.0	459.8	468.4
Selling, general and administrative expenses		32.4	23.3	90.6	62.3
Research and development expenses		7.5	7.2	18.3	19.4
Restructuring charges, net			0.0	0.0	0.0
Operating (loss) income		51.1	42.0	154.6	119.7
Operating Segments | Sterile Injectables
Segment Reporting Information
Net sales		47.2	0.0	47.2	0.0
Cost of sales		56.9	0.0	56.9	0.0
Selling, general and administrative expenses		5.1	0.0	5.1	0.0
Research and development expenses		7.4	0.0	7.4	0.0
Restructuring charges, net			0.0	0.0	0.0
Operating (loss) income		(22.2)	0.0	(22.2)	0.0
Corporate, Non-Segment
Segment Reporting Information
Cost of sales		5.0	3.6	12.6	10.9
Selling, general and administrative expenses		198.8	54.2	320.3	154.6
Research and development expenses		13.3	10.3	31.0	$ 29.7
Combination, integration, and other related expenses		93.8		136.9
Liabilities management and separation costs		$ 33.3	$ 15.2	$ 36.9