Post-Retirement Health Care (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Apr. 01, 2017
Retirement Benefits [Abstract]
Service cost	$ 213	$ 185
Interest cost	197	206
Amortization of net (gain) loss	37	7
Net periodic post-retirement benefit cost	$ 447	$ 398

No definition available.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

+ References

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Amount of cost recognized for passage of time related to defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
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Amount of net periodic benefit cost (credit) for defined benefit plan.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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-Name Accounting Standards Codification
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