Equity (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 27, 2014		Jun. 28, 2013		Jun. 27, 2014		Jun. 28, 2013
Pension and other post-retirement benefit cost [Abstract]
Amortization of net loss, before tax	$ 1,811	[1]	$ 2,714	[1]	$ 3,815	[1]	$ 5,387	[1]
Amortization of net loss, tax	(132)	[1]	(213)	[1]	(305)	[1]	(354)	[1]
Amortization of net loss, net of tax	1,679	[1]	2,501	[1]	3,510	[1]	5,033	[1]
Amortization of prior service cost, before tax	62	[1]	62	[1]	124	[1]	124	[1]
Amortization of prior service cost, tax	0	[1]	0	[1]	0	[1]	0	[1]
Amortization of prior service cost, net of tax	62	[1]	62	[1]	124	[1]	124	[1]
Total amount reclassified from Accumulated other comprehensive income (loss), before tax	1,873		2,776		3,939		5,511
Total amount reclassified from Accumulated other comprehensive income (loss), tax	(132)		(213)		(305)		(354)
Total amount reclassified from Accumulated other comprehensive income (loss), net of tax	$ 1,741		$ 2,563		$ 3,634		$ 5,157

[1] Included in the computation of net periodic benefit (income) cost. See Note 11, “Net Periodic Benefit Cost - Defined Benefit Plans” for additional details.