Fresh-Start Accounting - Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jul. 01, 2022	Jun. 16, 2022	Apr. 01, 2022	Dec. 31, 2021	Sep. 24, 2021	Jun. 25, 2021	Mar. 26, 2021	Dec. 25, 2020
Reorganization, Chapter 11 [Line Items]
Cash and cash equivalents	$ 391.2		$ 297.9		$ 1,345.0	$ 1,322.6
Accounts receivable, less allowance for doubtful accounts of $6.0 and $4.7	377.0				439.1
Inventories	1,071.6				347.2
Prepaid expenses and other current assets	321.4				178.3
Assets Held-for-sale, Not Part of Disposal Group, Current	7.2				0.0
Assets, Current	2,168.4				2,309.6
Property, plant and equipment, net	448.3				776.0
Intangible assets, net	2,980.4				5,448.4
Other assets	196.1				382.3
Assets	6,257.4				8,916.3
Current maturities of long-term debt	44.1				1,388.9
Accounts payable	89.1				123.0
Accrued payroll and payroll-related costs	40.7				84.6
Accrued interest	71.1				17.0
Medicaid lawsuit liability	16.5		260.0		0.0
Opioid-Related Litigation Settlement liability, Current	200.0				0.0
Accrued and other current liabilities	317.6				328.7
Liabilities, Current	779.1				1,942.2
Long-term debt	3,034.3				0.0
Acthar Gel-Related Settlement, Non-current	69.2				0.0
Opioid-Related Litigation Settlement liability	342.8				0.0
Pension and postretirement benefits	53.6				30.1
Environmental liabilities	36.4				43.0
Deferred Tax Liabilities, Gross	1.5				20.9
Other income tax liabilities	14.4				83.2
Other liabilities	77.0				85.8
Liabilities subject to compromise	0.0				6,397.7
Liabilities	4,408.3				8,602.9
Treasury Stock, Value	0.0				1,616.1
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding	2,204.0				5,597.8
Predecessor ordinary shares held in treasury at cost, none and 9,569,645	(6.4)				(8.3)
Retained deficit	(348.6)				(3,678.9)
Stockholders' Equity Attributable to Parent	1,849.1	$ 2,138.2	2,203.6	$ 195.0	313.4	$ 513.4	$ 776.0	$ 878.9	$ 1,019.2
Liabilities and Equity	6,257.4				8,916.3
Predecessor
Reorganization, Chapter 11 [Line Items]
Preferred shares	0.0				0.0
Ordinary A shares	0.0				0.0
Ordinary shares	0.0				18.9
Successor
Reorganization, Chapter 11 [Line Items]
Preferred shares	0.0				0.0
Ordinary A shares	0.0				0.0
Ordinary shares	$ 0.1				$ 0.0
Reorganization, Chapter 11, Predecessor, before Adjustment
Reorganization, Chapter 11 [Line Items]
Cash and cash equivalents			1,392.6
Accounts receivable, less allowance for doubtful accounts of $6.0 and $4.7			387.4
Inventories			375.2
Prepaid expenses and other current assets			322.6
Assets Held-for-sale, Not Part of Disposal Group, Current			0.0
Assets, Current			2,477.8
Property, plant and equipment, net			748.6
Intangible assets, net			5,166.6
Deferred Tax Assets, Net			0.0
Other assets			222.8
Assets			8,615.8
Current maturities of long-term debt			1,389.9
Accounts payable			156.4
Accrued payroll and payroll-related costs			71.4
Accrued interest			20.8
Medicaid lawsuit liability			0.0
Opioid-Related Litigation Settlement liability, Current			0.0
Accrued and other current liabilities			296.1
Liabilities Held-for-Sales, Not Part of Disposal Group, Current			0.0
Liabilities, Current			1,934.6
Long-term debt			0.0
Acthar Gel-Related Settlement, Non-current			0.0
Opioid-Related Litigation Settlement liability			0.0
Pension and postretirement benefits			27.6
Environmental liabilities			37.1
Deferred Tax Liabilities, Gross			20.4
Other income tax liabilities			75.9
Other liabilities			68.6
Liabilities subject to compromise			6,402.7
Liabilities			8,566.9
Preferred shares			0.0
Ordinary A shares			0.0
Treasury Stock, Value			1,616.1
Predecessor ordinary shares held in treasury at cost, none and 9,569,645			(9.9)
Retained deficit			(3,943.5)
Stockholders' Equity Attributable to Parent			48.9
Liabilities and Equity			8,615.8
Reorganization, Chapter 11, Predecessor, before Adjustment | Predecessor
Reorganization, Chapter 11 [Line Items]
Ordinary shares			18.9
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding			5,599.5
Reorganization, Chapter 11, Predecessor, before Adjustment | Successor
Reorganization, Chapter 11 [Line Items]
Ordinary shares			0.0
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding			0.0
Reorganization, Chapter 11, Plan Effect Adjustment
Reorganization, Chapter 11 [Line Items]
Cash and cash equivalents			(1,094.7)
Accounts receivable, less allowance for doubtful accounts of $6.0 and $4.7			0.0
Inventories			0.0
Prepaid expenses and other current assets			75.3
Assets Held-for-sale, Not Part of Disposal Group, Current			0.0
Assets, Current			(1,019.4)
Property, plant and equipment, net			0.0
Intangible assets, net			0.0
Deferred Tax Assets, Net			0.0
Other assets			(3.9)
Assets			(1,023.3)
Current maturities of long-term debt			(1,355.2)
Accounts payable			(53.8)
Accrued payroll and payroll-related costs			0.0
Accrued interest			(13.0)
Medicaid lawsuit liability			16.5
Opioid-Related Litigation Settlement liability, Current			200.0
Accrued and other current liabilities			50.8
Liabilities Held-for-Sales, Not Part of Disposal Group, Current			35.0
Liabilities, Current			(1,119.7)
Long-term debt			3,050.9
Acthar Gel-Related Settlement, Non-current			63.2
Opioid-Related Litigation Settlement liability			304.3
Pension and postretirement benefits			27.2
Environmental liabilities			0.0
Deferred Tax Liabilities, Gross			102.7
Other income tax liabilities			0.0
Other liabilities			23.6
Liabilities subject to compromise			(6,402.7)
Liabilities			(3,950.5)
Preferred shares			0.0
Ordinary A shares			0.0
Treasury Stock, Value			(1,616.1)
Predecessor ordinary shares held in treasury at cost, none and 9,569,645			0.0
Retained deficit			4,725.9
Stockholders' Equity Attributable to Parent			2,927.2
Liabilities and Equity			(1,023.3)
Reorganization, Chapter 11, Plan Effect Adjustment | Predecessor
Reorganization, Chapter 11 [Line Items]
Ordinary shares			(18.9)
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding			(5,599.5)
Reorganization, Chapter 11, Plan Effect Adjustment | Successor
Reorganization, Chapter 11 [Line Items]
Ordinary shares			0.1
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding			2,203.5
Reorganization, Chapter 11, Fresh-Start Adjustment
Reorganization, Chapter 11 [Line Items]
Cash and cash equivalents			0.0
Accounts receivable, less allowance for doubtful accounts of $6.0 and $4.7			0.0
Inventories			851.8
Prepaid expenses and other current assets			(58.3)
Assets Held-for-sale, Not Part of Disposal Group, Current			100.0
Assets, Current			893.5
Property, plant and equipment, net			(299.2)
Intangible assets, net			(2,014.4)
Deferred Tax Assets, Net			453.4
Other assets			(23.5)
Assets			(990.2)
Current maturities of long-term debt			0.0
Accounts payable			0.0
Accrued payroll and payroll-related costs			0.0
Accrued interest			0.0
Medicaid lawsuit liability			0.0
Opioid-Related Litigation Settlement liability, Current			0.0
Accrued and other current liabilities			(6.1)
Liabilities Held-for-Sales, Not Part of Disposal Group, Current			0.0
Liabilities, Current			(6.1)
Long-term debt			(18.4)
Acthar Gel-Related Settlement, Non-current			0.0
Opioid-Related Litigation Settlement liability			0.0
Pension and postretirement benefits			0.0
Environmental liabilities			0.0
Deferred Tax Liabilities, Gross			(121.7)
Other income tax liabilities			(61.9)
Other liabilities			(9.6)
Liabilities subject to compromise			0.0
Liabilities			(217.7)
Preferred shares			0.0
Ordinary A shares			0.0
Treasury Stock, Value			0.0
Predecessor ordinary shares held in treasury at cost, none and 9,569,645			9.9
Retained deficit			(782.4)
Stockholders' Equity Attributable to Parent			(772.5)
Liabilities and Equity			(990.2)
Reorganization, Chapter 11, Fresh-Start Adjustment | Predecessor
Reorganization, Chapter 11 [Line Items]
Ordinary shares			0.0
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding			0.0
Reorganization, Chapter 11, Fresh-Start Adjustment | Successor
Reorganization, Chapter 11 [Line Items]
Ordinary shares			0.0
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding			0.0
Reorganization, Chapter11, Post Adjustment, Successor
Reorganization, Chapter 11 [Line Items]
Cash and cash equivalents			297.9
Accounts receivable, less allowance for doubtful accounts of $6.0 and $4.7			387.4
Inventories			1,227.0
Prepaid expenses and other current assets			339.6
Assets Held-for-sale, Not Part of Disposal Group, Current			100.0
Assets, Current			2,351.9
Property, plant and equipment, net			449.4
Intangible assets, net			3,152.2
Deferred Tax Assets, Net			453.4
Other assets			195.4
Assets			6,602.3
Current maturities of long-term debt			34.7
Accounts payable			102.6
Accrued payroll and payroll-related costs			71.4
Accrued interest			7.8
Medicaid lawsuit liability			16.5
Opioid-Related Litigation Settlement liability, Current			200.0
Accrued and other current liabilities			340.8
Liabilities Held-for-Sales, Not Part of Disposal Group, Current			35.0
Liabilities, Current			808.8
Long-term debt			3,032.5
Acthar Gel-Related Settlement, Non-current			63.2
Opioid-Related Litigation Settlement liability			304.3
Pension and postretirement benefits			54.8
Environmental liabilities			37.1
Deferred Tax Liabilities, Gross			1.4
Other income tax liabilities			14.0
Other liabilities			82.6
Liabilities subject to compromise			0.0
Liabilities			4,398.7
Preferred shares			0.0
Ordinary A shares			0.0
Treasury Stock, Value			0.0
Predecessor ordinary shares held in treasury at cost, none and 9,569,645			0.0
Retained deficit			0.0
Stockholders' Equity Attributable to Parent			2,203.6
Liabilities and Equity			6,602.3
Reorganization, Chapter11, Post Adjustment, Successor | Predecessor
Reorganization, Chapter 11 [Line Items]
Ordinary shares			0.0
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding			0.0
Reorganization, Chapter11, Post Adjustment, Successor | Successor
Reorganization, Chapter 11 [Line Items]
Ordinary shares			0.1
Predecessor ordinary shares, $0.20 par value, 500,000,000 authorized; 94,296,235 issued; 84,726,590 outstanding			$ 2,203.5