Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 28, 2015	Mar. 29, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss - interest rate swaps	$ (1,841)
Accumulated other comprehensive - postretirement liabilities	328
Accumulated other comprehensive loss - total	(1,513)
Unrealized loss on interest rate swaps	(1,014)	(582)
Reclassification of loss into earnings from interest rate swaps	83	53
Reclassification of net actuarial gain into earnings from postretirement benefit plans	(5)	(6)
Reclassification of prior service credits into earnings from postretirement benefit plans	(13)	(14)
Accumulated other comprehensive loss - interest rate swaps	(2,772)
Accumulated other comprehensive - postretirement liabilities	310
Accumulated other comprehensive loss - total	(2,462)
Unrealized gain (loss) on interest rate swaps - income taxes	(621)	(358)
Reclassification of loss into earnings from interest rate swaps - income taxes	51	33
Reclassification of net actuarial gain into earnings from postretirement benefit plans - income taxes	(4)	(4)
Reclassification of prior service credits into earnings from postretirement benefit plans - income taxes	$ (9)	$ (8)