GOODWILL AND INTANGIBLE ASSETS - Carrying Values of Trade Names - (Details) - USD ($)	3 Months Ended
Mar. 26, 2022	Dec. 25, 2021
Newmark
Non-amortized intangible assets
Carrying value of trade names	$ 11,111,000	$ 11,111,000
Convert Italia S.p.A
Non-amortized intangible assets
Carrying value of trade names	8,238,000	8,479,000
Webforge
Non-amortized intangible assets
Carrying value of trade names	7,747,000	7,877,000
Ingal EPS/Ingal Civil Products
Non-amortized intangible assets
Carrying value of trade names	7,511,000	7,637,000
Valmont SM
Non-amortized intangible assets
Carrying value of trade names	5,904,000	6,082,000
Shakespeare
Non-amortized intangible assets
Carrying value of trade names	4,000,000	4,000,000
Walpar
Non-amortized intangible assets
Carrying value of trade names	3,500,000	3,500,000
Other
Non-amortized intangible assets
Carrying value of trade names	14,729,000	14,721,000
Trade Names
Non-amortized intangible assets
Carrying value of trade names	62,740,000	$ 63,407,000
Impairment indefinite-lived intangible assets	$ 0

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=123570139&loc=d3e3602-108585

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

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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