Retirement Plans (Schedule of Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 25, 2020
Amounts recognized on the consolidated balance sheet:
Pension and postretirement benefits	$ 30.1	$ 34.6
Pension Benefits
Amounts recognized on the consolidated balance sheet:
Current liabilities	0.8	0.8
Pension and postretirement benefits	16.7	18.9
Liability Subject to Compromise, Pension and Other Postretirement Benefit Plan, Benefit Obligation	9.8	9.7
Net amount recognized on the consolidated balance sheet	27.3	29.4
Amounts recognized in accumulated other comprehensive loss consist of:
Net actuarial loss	(9.7)	(11.8)
Prior service (cost) credit	0.0	(0.1)
Net amount recognized in accumulated other comprehensive loss	(9.7)	(11.9)
Postretirement Benefits
Amounts recognized on the consolidated balance sheet:
Current liabilities	1.7	1.9
Pension and postretirement benefits	13.4	15.5
Liability Subject to Compromise, Pension and Other Postretirement Benefit Plan, Benefit Obligation	22.2	22.7
Net amount recognized on the consolidated balance sheet	37.3	40.1
Amounts recognized in accumulated other comprehensive loss consist of:
Net actuarial loss	(0.1)	(2.0)
Prior service (cost) credit	1.7	3.8
Net amount recognized in accumulated other comprehensive loss	$ 1.6	$ 1.8