Retirement Plans (Summary of Net Pension and Supplemental Executive Retirement Plan Expense Recognized) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 20, 2015	Jun. 14, 2014	Jun. 20, 2015	Jun. 14, 2014
Compensation and Retirement Disclosure [Abstract]
Service cost pertaining to benefits earned during the period	$ 2.1	$ 1.6	$ 4.2	$ 3.3
Interest cost on projected benefit obligations	4.3	4.6	8.5	9.3
Expected return on pension assets	(4.8)	(5.1)	(9.5)	(10.2)
Net amortization loss	4.9	1.8	9.7	3.5
Net pension expense	$ 6.5	$ 2.9	$ 12.9	$ 5.9