Retirement Plans (Narrative) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)	Dec. 26, 2015 USD ($)
Retirement Plans [Abstract]
Number of supplemental retirement plans	3
Defined Benefit Plan, Benefit Obligation	$ 6,077
Retirement Plans, Accumulated Benefit Obligation	$ 11,176	$ 9,079
Deferred Compensation Arrangement with Individual, Requisite Service Period	6 years

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Projected Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6522206

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accumulated Postretirement Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6503904

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant