Postretirement Benefits Amounts Recognized in Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 28, 2014	Dec. 29, 2013
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	$ 2,682	$ 3,037
Net gain	(2,595)	(1,891)
Deferred Tax Liabilities, Other Comprehensive Income	(34)	(444)
Accumulated other comprehensive income	(357)	702
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year	160
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year	(355)
Other Comprehensive Income (Loss) [Member]
Defined Benefit Plan Disclosure [Line Items]
Deferred Tax Liabilities, Other Comprehensive Income	$ (444)