Other Postretirement Benefits - Schedule of Components of Net Periodic Postretirement Benefit Income (Details) - Other Postretirement Benefit Plans [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 367	$ 417	$ 588
Interest cost	1,881	1,979	2,794
Amortization and other costs	3,621	4,105	5,197
Amortization of prior service credit	(7,755)	(8,440)	(9,495)
Effect of settlement/curtailment (1)	(32,737)	0	0
Net periodic pension cost	$ (34,623)	$ (1,939)	$ (916)