Other Postretirement Benefits - Changes in the Benefit Obligation and Plan Assets and Other Amounts (Details) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 28, 2014	Dec. 29, 2013	Dec. 30, 2012
Other Postretirement Benefit Plans, Defined Benefit [Member]
Change in benefit obligation
Benefit obligation at beginning of year	$ 100,932	$ 120,767
Service cost	580	1,089	957
Interest cost	3,722	4,101	4,985
Plan participants’ contributions	3,834	4,861
Actuarial loss/(gain)	12,091	(13,501)
Plan amendments	(25,489)	(1,690)
Benefits paid	(14,616)	(14,695)
Benefit obligation at end of year	81,054	100,932	120,767
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Employer contributions	10,782	9,834
Plan participants’ contributions	3,834	4,861
Benefits paid	(14,616)	(14,695)
Fair value of plan assets at end of year	0	0	0
Amount recognized in the Consolidated Balance Sheets
Current liabilities	(9,426)	(10,329)
Noncurrent liabilities	(71,628)	(90,603)
Net amount recognized	(81,054)	(100,932)
Amount recognized in accumulated other comprehensive loss
Actuarial loss	37,339	33,406
Prior service cost	(51,950)	(33,660)
Total amount recognized in accumulated other comprehensive loss	$ (14,611)	$ (254)