ACQUISITIONS - Narrative (Details) $ in Thousands, $ in Thousands				3 Months Ended			12 Months Ended
	Aug. 31, 2023 USD ($) payment	Aug. 31, 2023 AUD ($)	Jun. 01, 2022 USD ($)	Mar. 30, 2024 USD ($)	Sep. 24, 2022 USD ($)	Jun. 25, 2022 USD ($)	Dec. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 28, 2024 USD ($)	Aug. 31, 2023 AUD ($) payment
Business Acquisition [Line Items]
Acquisitions, net of cash acquired							$ 32,676	$ 39,287
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Goodwill							632,964	$ 739,861	$ 623,847
Operating lease liabilities							182,296		156,980
Redeemable noncontrolling interest							$ 62,792		$ 51,519
HR Products
Business Acquisition [Line Items]
Acquisitions, net of cash acquired	$ 37,302	$ 58,044
Retention fund, withheld	$ 4,626									$ 7,200
Number of equal payments of retention fund | payment	2									2
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Current assets	$ 24,153
Property, plant, and equipment	1,397
Goodwill	9,508
Other non-current assets	3,997
Total fair value of assets acquired	50,558
Current liabilities	4,183
Deferred income taxes	3,046
Operating lease liabilities	2,792
Total fair value of liabilities assumed	10,021
Net assets acquired	$ 40,537
ConcealFab
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Current assets			$ 21,133
Property, plant, and equipment			3,813
Goodwill			42,465
Other non-current assets			9,108
Total fair value of assets acquired			107,719
Current liabilities			6,658
Long-term debt			2,038
Deferred income taxes			5,464
Operating lease liabilities			7,812
Other non-current liabilities			12
Total fair value of liabilities assumed			21,984
Redeemable noncontrolling interest			41,693
Net assets acquired			$ 44,042
Percentage acquired			51.00%	9.00%
Cash paid to acquire business			$ 39,287
Consideration transferred				$ 7,227
Contingent consideration liability, current			1,850
Valmont Substations, LLC
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Consideration transferred				$ 10,518
Convert Italia S.p.A.
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Percentage acquired					9.00%
Consideration transferred					$ 3,046
Valmont West Coast Engineering
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Percentage acquired						20.00%
Consideration transferred						$ 4,292
Customer relationships
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Useful life	13 years	13 years
Customer relationships | HR Products
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Customer relationships	$ 11,503
Customer relationships | ConcealFab
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Customer relationships			26,200
Trade names | ConcealFab
Fair Values of Assets Acquired and Liabilities Assumed [Abstract]
Customer relationships			$ 5,000