CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE LOSS (Parenthetical) - USD ($)	3 Months Ended	6 Months Ended
Jul. 01, 2018	Jun. 25, 2017	Jul. 01, 2018	Jun. 25, 2017
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Change in pension and post-retirement benefit plans, taxes	$ 0	$ (1,714,000)	$ 0	$ (3,428,000)
Other comprehensive income, taxes	$ 0	$ (2,649,000)	$ 0	$ (2,697,000)

Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income for defined benefit plan, attributable to parent.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=84161450&loc=SL4573702-111684

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569616-111683

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569643-111683

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration