Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 24, 2021	Sep. 25, 2020	Sep. 24, 2021	Sep. 25, 2020	Dec. 25, 2020
Income Taxes [Line Items]
Income tax benefit	$ (32.0)	$ (211.6)	$ (81.9)	$ (69.2)
Increase (decrease) tax benefit	$ (179.6)		$ (12.7)
Effective tax rate	10.60%	1068.70%	13.60%	7.80%
Current Income Tax Expense (Benefit)	$ 26.2	$ 201.4	$ (62.8)	$ (370.3)
Deferred Income Tax Expense (Benefit)	5.8	10.2	(19.1)	(301.1)
Income Taxes Paid, Net				42.9
Unrecognized tax benefits	334.2		334.2		$ 349.0
Unrecognized tax benefits, net increase			(14.8)
Unrecognized tax benefits, which if favorably settled would benefit the effective tax rate	63.2		63.2
Interest accrued on unrecognized tax benefits	17.9		17.9		$ 16.7
Unrecognized tax benefits that would impact effective tax rate, upper bound of change	139.9		139.9
Income tax penalties and interest accrued that would impact effective tax rate, upper bound of change	16.4		16.4
Increase (Decrease) Tax Expense (Benefit), Change in Operating Income	12.6		56.2
Increase (Decrease), Tax Expense (Benefit), CARES Act	236.8		(285.5)
Increase (Decrease), Tax Expense (Benefit), Uncertain Tax Positions	7.9		2.8
Increase (Decrease), Income Tax Expense (Benefit), Separation Costs, Reorganization Items, and Restructuring Charges	4.7		10.8
Increase (Decrease) Tax Benefit, Intercompany Financing Reorganization	32.0		(25.7)
Increase (Decrease), Tax Expense (Benefit), Valuation Allowances			202.7
Proceeds from Income Tax Refunds			160.4
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities			0.2
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions			7.2
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations			21.8
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	5.3	(0.2)	6.0	23.8
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(301.0)	$ (19.8)	(601.3)	$ (884.7)
Nuclear Imaging
Income Taxes [Line Items]
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ 5.1
CARES Act [Member]
Income Taxes [Line Items]
Proceeds from Income Tax Refunds			178.8
Continuing Operations
Income Taxes [Line Items]
Income Taxes Paid, Net			$ 18.4