Shareholders' Equity and Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 26, 2014		Sep. 27, 2013		Sep. 26, 2014		Sep. 27, 2013		Jun. 27, 2014		Dec. 31, 2013		Jun. 28, 2013	Dec. 31, 2012
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation	$ (18,525)		$ (16,604)		$ (18,525)		$ (16,604)		$ (12,759)		$ (14,219)		$ (21,273)	$ (16,515)
Foreign currency translation adjustments	(5,766)		4,669		(4,306)		(89)
Reclassification to net income, foreign currency translation	0				0		0
Other Comprehensive Income (Loss), Foreign Currency Translation	(5,766)		4,669		(4,306)		(89)
Changes in pension and post-retirement benefit plans	(64,311)	[1]	(100,064)	[1]	(64,311)	[1]	(100,064)	[1]	(64,980)	[1]	(66,317)	[1]	101,600	104,551
Amortization of prior service cost, net of tax expense	14	[1]	15	[1]	42	[1]	45	[1]
Amortization of net loss, net of tax expense	655	[1]	1,521	[1]	1,964	[1]	4,442	[1]
Pension plan adjustments, net of tax expense	669	[1]	1,536	[1]	2,006	[1]	4,487	[1]
Accumulated Other Comprehensive Income (Loss), Unrealized Gain (Loss) on derivative instruments, Effect Net of Tax	(510)	[2]	(582)	[2]	(510)	[2]	(582)	[2]	(516)	[2]	(585)	[2]	(463)	(524)	[2]
Net loss on derivative instruments, net of tax expense (benefit)	(104)	[2]	(158)	[2]	(233)	[2]	(114)	[2]
Reclassification to net income, derivative instruments, net of tax benefit	110	[2]	39		308	[2]	56	[2]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	6	[2]	(119)	[2]	75	[2]	(58)	[2]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(83,346)		(117,250)		(83,346)		(117,250)				(81,121)
Tax expense for pension plan adjustments	405		941		1,215		2,751
Tax expense (benefit) for the change in unrealized loss on derivative instruments	62		98		140		71
Tax expense (benefit) on loss on derivative instruments reclassified to net income	68		24		187		35
Amortization of prior service cost
Schedule of Accumulated Other Comprehensive Income [Line Items]
Tax expense for pension plan adjustments	9		10		26		30
Amortization of net loss
Schedule of Accumulated Other Comprehensive Income [Line Items]
Tax expense for pension plan adjustments	$ 396		$ 931		$ 1,189		$ 2,721

[1] These accumulated other comprehensive income components are included in the computation of net periodic pension cost. (See Note 10, Pension Plans for additional information.)

[2] See Note 7, Derivative Financial Instruments, for additional information regarding our derivative instruments.