Financial Instruments and Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 30, 2022	Jun. 16, 2022	Dec. 31, 2021	Dec. 25, 2020
Carrying Value | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash	$ 57.2		$ 60.2
Carrying Value | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash surrender value of life insurance	46.7		51.3
Restricted Cash and Investments, Current	20.6	$ 113.0	24.0	$ 20.2
Restricted Cash and Investments, Noncurrent	36.6	36.4	36.2	36.2
Professional Fees Escrow Account
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash	0.0	89.0
Silence Therapeutics [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Investments	(9.2)	$ (22.2)	(4.7)	(3.8)
Debentures | 8.00% debentures due March 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		8.00%
Debentures | 8.00% debentures due March 2023 | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		8.00%
Debentures | 9.50% debentures due May 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		9.50%
Debentures | 9.50% debentures due May 2022 | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		9.50%
Senior Notes | 4.75% senior notes due April 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		4.75%
Senior Notes | 4.75% senior notes due April 2023 | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		4.75%
Senior Notes | Five Point Five Percent Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		5.50%
Senior Notes | Five Point Five Percent Notes [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		5.50%
Senior Notes | 5.75% senior notes due August 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		5.75%
Senior Notes | 5.75% senior notes due August 2022 | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		5.75%
Debentures | Five Point Six Two Five Percent Note
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		5.625%
Debentures | Five Point Six Two Five Percent Note | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate		5.625%
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of contingent consideration upon acquisition	7.3		27.3
Debt and equity securities held in rabbi trusts	36.6		38.7
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of contingent consideration upon acquisition	0.0		0.0
Debt and equity securities held in rabbi trusts	24.8		24.9
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of contingent consideration upon acquisition	0.0		0.0
Debt and equity securities held in rabbi trusts	11.8		13.8
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of contingent consideration upon acquisition	7.3		27.3
Debt and equity securities held in rabbi trusts	$ 0.0		0.0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 | Stratatech [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability			$ 27.3
Nuclear Imaging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration received, equity certificates				$ 9.0