Fresh-Start Accounting - Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Jul. 01, 2022	Jun. 16, 2022	Apr. 01, 2022	Dec. 31, 2021	Jun. 25, 2021	Mar. 26, 2021	Dec. 25, 2020
Reorganization, Chapter 11 [Line Items]
Cash and cash equivalents	$ 354.7	$ 297.9		$ 1,345.0	$ 1,254.9
Accounts receivable, less allowance for doubtful accounts of $5.8 and $4.7	370.4			439.1
Inventories	1,201.2			347.2
Prepaid expenses and other current assets	344.2			178.3
Assets, Current	2,270.5			2,309.6
Property, plant and equipment, net	448.2			776.0
Intangible assets, net	3,106.7			5,448.4
Other assets	200.7			382.3
Assets	6,485.9			8,916.3
Current maturities of long-term debt	44.1			1,388.9
Accounts payable	89.4			123.0
Accrued payroll and payroll-related costs	63.9			84.6
Accrued interest	21.2			17.0
Medicaid lawsuit liability	16.5			0.0
Opioid-Related Litigation Settlement liability, Current	200.0			0.0
Accrued and other current liabilities	326.5			328.7
Liabilities, Current	761.6			1,942.2
Long-term debt	3,025.5			0.0
Acthar Gel-Related Settlement, Non-current	67.2			0.0
Opioid-Related Litigation Settlement liability	307.6			0.0
Pension and postretirement benefits	54.8			30.1
Environmental liabilities	37.2			43.0
Deferred Tax Liabilities, Gross	1.4			20.9
Other income tax liabilities	14.0			83.2
Other liabilities	78.4			85.8
Liabilities subject to compromise	0.0			6,397.7
Liabilities	4,347.7			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	2,203.5			5,597.8
Predecessor ordinary shares held in treasury at cost, none and 9,569,645	(1.7)			(8.3)
Retained deficit	(63.7)			(3,678.9)
Stockholders' Equity Attributable to Parent	2,138.2	2,203.6	$ 195.0	313.4	$ 776.0	$ 878.9	$ 1,019.2
Liabilities and Equity	6,485.9			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 $5.8 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 $5.8 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 $5.8 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 $5.8 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