Other Postretirement Benefits - Schedule of Components of Net Periodic Postretirement Benefit Income (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 25, 2016	Dec. 27, 2015	Dec. 28, 2014
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 417	$ 588	$ 580
Interest cost	1,979	2,794	3,722
Amortization and other costs	4,105	5,197	7,299
Amortization of prior service credit	(8,440)	(9,495)	(7,199)
Net periodic postretirement benefit (income)/expense	$ (1,939)	$ (916)	$ 4,402