Retirement Plans (Summary of Net Pension and Supplemental Executive Retirement Plan Expense Recognized) (Details) - USD ($) $ in Millions	3 Months Ended		8 Months Ended
	Sep. 12, 2015	Sep. 06, 2014	Sep. 12, 2015	Sep. 06, 2014
Compensation and Retirement Disclosure [Abstract]
Service cost pertaining to benefits earned during the period	$ 2.1	$ 1.7	$ 6.3	$ 5.0
Interest cost on projected benefit obligations	4.2	4.8	12.7	14.1
Expected return on pension assets	(4.7)	(5.2)	(14.2)	(15.4)
Net amortization loss	4.8	1.7	14.5	5.2
Net pension expense	$ 6.4	$ 3.0	$ 19.3	$ 8.9