Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Number of Trade Names Impaired

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GOODWILL AND INTANGIBLE ASSETS - Carrying Values of Trade Names - (Details)	3 Months Ended	12 Months Ended
	Sep. 26, 2020 USD ($)	Dec. 26, 2020 USD ($) tradeName	Mar. 27, 2021 USD ($)
Non-amortized intangible assets
Number of trade names impaired \| tradeName		2
Newmark
Non-amortized intangible assets
Carrying value of trade names		$ 11,111,000	$ 11,111,000
Webforge
Non-amortized intangible assets
Carrying value of trade names		7,972,000	8,104,000
Convert Italia S.p.A
Non-amortized intangible assets
Carrying value of trade names		9,137,000	8,845,000
Valmont SM
Non-amortized intangible assets
Carrying value of trade names		8,720,000	8,443,000
Ingal EPS/Ingal Civil Products
Non-amortized intangible assets
Carrying value of trade names		7,730,000	7,857,000
Walpar
Non-amortized intangible assets
Carrying value of trade names		3,500,000	3,500,000
Shakespeare
Non-amortized intangible assets
Carrying value of trade names		4,000,000	4,000,000
Other
Non-amortized intangible assets
Carrying value of trade names		14,828,000	14,925,000
Trade Names
Non-amortized intangible assets
Carrying value of trade names		66,998,000	$ 66,785,000
Impairment indefinite-lived intangible assets	$ 0	$ 3,900,000