Retirement Plans (Schedule of Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 27, 2019	Dec. 28, 2018
Amounts recognized on the consolidated balance sheet:
Non-current liabilities	$ (62.4)	$ (60.5)
Pension Benefits
Amounts recognized on the consolidated balance sheet:
Current liabilities	(1.8)	(2.0)
Non-current liabilities	(25.2)	(24.1)
Net amount recognized on the consolidated balance sheet	(27.0)	(26.1)
Amounts recognized in accumulated other comprehensive loss consist of:
Net actuarial (loss) gain	(10.1)	(8.4)
Prior service (cost) credit	(0.2)	(0.4)
Net amount recognized in accumulated other comprehensive loss	(10.3)	(8.8)
Postretirement Benefits
Amounts recognized on the consolidated balance sheet:
Current liabilities	(3.3)	(3.4)
Non-current liabilities	(37.2)	(36.4)
Net amount recognized on the consolidated balance sheet	(40.5)	(39.8)
Amounts recognized in accumulated other comprehensive loss consist of:
Net actuarial (loss) gain	(0.8)	0.9
Prior service (cost) credit	5.9	8.1
Net amount recognized in accumulated other comprehensive loss	$ 5.1	$ 9.0

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount, after tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, after tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as current.

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Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent.

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