Shareholders' Equity - Postretirement medical adjustments reclassified to pension cost (Details) - Pension and Post- retirement Medical - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 23, 2016	Sep. 25, 2015	Sep. 23, 2016	Sep. 25, 2015
Reclassification from AOCI
Reclassification before tax	$ 1,707	$ 2,537	$ 4,957	$ 6,894
Income tax (benefit)	(619)	(837)	(1,823)	(2,478)
Reclassification after tax	1,088	1,700	3,134	4,416
Cost of products sold
Reclassification from AOCI
Reclassification before tax	611	959	1,776	2,604
Product development
Reclassification from AOCI
Reclassification before tax	241	418	706	1,120
Selling, marketing and distribution
Reclassification from AOCI
Reclassification before tax	578	718	1,633	1,950
General and administrative
Reclassification from AOCI
Reclassification before tax	$ 277	$ 442	$ 842	$ 1,220

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

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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=66004124&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=66004921&loc=d3e1436-108581

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65896914&loc=d3e39076-109324

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

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