Retirement Plans (Retirement Plan Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension Expense	$ 5,574	$ 3,162	$ 5,171
Retirement savings plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Expense	3,593	3,161	3,010
Deferred compensation plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Expense	788	(318)	1,328
Supplemental executive retirement plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Expense	909	484	1,061
Deferred compensation plan for pharmacists [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Expense	$ 284	$ (165)	$ (228)