Shareholders' Equity - Changes in components of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 24, 2016	Jun. 26, 2015	Jun. 24, 2016	Jun. 26, 2015
Pension and Post- retirement Medical
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (69,018)	$ (75,048)	$ (69,922)	$ (76,584)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	1,142	1,180	2,046	2,716
Ending balance	(67,876)	(73,868)	(67,876)	(73,868)
Cumulative Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(36,977)	(27,163)	(34,575)	(24,152)
Other comprehensive income before reclassifications	(7,635)	12,404	(10,037)	9,393
Amounts reclassified from accumulated other comprehensive income	0	0
Ending balance	(44,612)	(14,759)	(44,612)	(14,759)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(105,995)	(102,211)	(104,497)	(100,736)
Other comprehensive income before reclassifications	(7,635)	12,404	(10,037)	9,393
Amounts reclassified from accumulated other comprehensive income	1,142	1,180	2,046	2,716
Ending balance	$ (112,488)	$ (88,627)	$ (112,488)	$ (88,627)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount after tax, before reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=51821188&loc=d3e1436-108581

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580

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- Definition

Amount after tax of reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=51821188&loc=d3e1436-108581

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- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

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