Retirement and Post Retirement Health Care Plans (Schedule Of Fair Value Of Plan Assets) (Details) - USD ($) $ in Millions	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 203.4	$ 174.0
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	113.1	94.6
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	8.3	0.0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	9.9	10.3	$ 9.6
Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	72.1	69.1
Net Asset Value | Common Collective Trust Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	72.1	61.7
Net Asset Value | Global Emerging Markets Fund Limited Partnership
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	7.4
Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5.1	3.9
Cash and Cash Equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Cash and Cash Equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Common Stock | Level 1 | Domestic Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	26.4	22.4
Common Stock | Level 1 | International Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	19.2	13.7
Common Stock | Level 2 | Domestic Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Common Stock | Level 2 | International Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Common Stock | Level 3 | Domestic Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Common Stock | Level 3 | International Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Limited Liability Company
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	8.3
Mutual Funds | Level 1 | US Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	30.1	24.8
Mutual Funds | Level 1 | International Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	3.1	2.5
Mutual Funds | Level 1 | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	9.5	8.5
Mutual Funds | Level 1 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	18.0	17.3
Mutual Funds | Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1.7	1.5
Mutual Funds | Level 1 | Limited Liability Company
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0
Mutual Funds | Level 1 | Real Estate Fund
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 2 | US Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 2 | International Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 2 | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 2 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 2 | Limited Liability Company
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	8.3
Mutual Funds | Level 2 | Real Estate Fund
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 3 | US Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 3 | International Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 3 | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 3 | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0	0.0
Mutual Funds | Level 3 | Limited Liability Company
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0.0
Mutual Funds | Level 3 | Real Estate Fund
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	9.9	10.3
Estimate of Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	131.3	104.9
Estimate of Fair Value | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5.1	3.9
Estimate of Fair Value | Common Stock | Domestic Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	26.4	22.4
Estimate of Fair Value | Common Stock | International Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	19.2	13.7
Estimate of Fair Value | Mutual Funds | US Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	30.1	24.8
Estimate of Fair Value | Mutual Funds | International Equity Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	3.1	2.5
Estimate of Fair Value | Mutual Funds | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	9.5	8.5
Estimate of Fair Value | Mutual Funds | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	18.0	17.3
Estimate of Fair Value | Mutual Funds | Other
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1.7	1.5
Estimate of Fair Value | Mutual Funds | Real Estate Fund
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 9.9	$ 10.3