General - Defined Benefit Plan (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 25, 2020	Jun. 27, 2019	Jun. 25, 2020	Jun. 27, 2019
General
Service cost	$ 273	$ 209	$ 547	$ 418
Interest cost	344	371	686	742
Net amortization of prior service cost and actuarial loss	247	109	495	218
Net periodic pension cost	$ 864	$ 689	$ 1,728	$ 1,378

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanServiceCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration