BUSINESS SEGMENTS (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2021 USD ($)	Jun. 27, 2020 USD ($)	Jun. 26, 2021 USD ($) segment	Jun. 27, 2020 USD ($)
Business Segments
Number of reportable segments | segment			4
Net sales	$ 894,629	$ 688,808	$ 1,669,515	$ 1,363,008
Operating income	82,625	43,440	159,836	110,335
Utility Support Structures Segment
Business Segments
Net sales	267,863	228,473	520,561	451,421
Operating income	14,955	21,650	36,607	49,374
Engineered Support Structures Segment
Business Segments
Net sales	269,340	248,873	491,496	476,239
Operating income	31,927	4,818	51,852	20,749
Coatings Segment
Business Segments
Net sales	77,605	62,667	149,196	131,257
Operating income	14,668	10,148	27,540	21,202
Irrigation Segment
Business Segments
Net sales	279,821	148,795	508,262	304,091
Operating income	41,984	22,351	80,732	46,014
Sales
Business Segments
Sales	917,375	715,353	1,715,787	1,416,361
Sales | Utility Support Structures Segment
Business Segments
Sales	267,863	231,324	520,996	456,785
Sales | Utility Support Structures Segment | Steel
Business Segments
Sales	176,974	159,817	345,471	326,348
Sales | Utility Support Structures Segment | Concrete
Business Segments
Sales	43,438	45,653	83,821	81,438
Sales | Utility Support Structures Segment | Engineered Solar Tracker Solutions
Business Segments
Sales	9,172	4,619	15,466	13,543
Sales | Utility Support Structures Segment | Offshore and Other Complex Steel Structures
Business Segments
Sales	38,279	21,235	76,238	35,456
Sales | Engineered Support Structures Segment
Business Segments
Sales	269,389	253,385	491,716	484,127
Sales | Engineered Support Structures Segment | Lighting, Traffic, and Highway Safety Products
Business Segments
Sales	186,973	181,027	340,843	353,014
Sales | Engineered Support Structures Segment | Communication Products
Business Segments
Sales	54,552	50,886	100,631	89,082
Sales | Engineered Support Structures Segment | Access Systems
Business Segments
Sales	27,864	21,472	50,242	42,031
Sales | Coatings Segment
Business Segments
Sales	98,158	80,005	191,446	168,090
Sales | Irrigation Segment
Business Segments
Sales	281,965	150,639	511,629	307,359
Intersegment sales
Business Segments
Sales	22,746	26,545	46,272	53,353
Intersegment sales | Utility Support Structures Segment
Business Segments
Sales	0	2,851	435	5,364
Intersegment sales | Engineered Support Structures Segment
Business Segments
Sales	49	4,512	220	7,888
Intersegment sales | Coatings Segment
Business Segments
Sales	20,553	17,338	42,250	36,833
Intersegment sales | Irrigation Segment
Business Segments
Sales	2,144	1,844	3,367	3,268
Other
Business Segments
Operating income	(20,909)	(15,527)	(36,895)	(27,004)
North America | Sales | Irrigation Segment
Business Segments
Sales	156,037	99,034	278,788	205,594
International | Sales | Irrigation Segment
Business Segments
Sales	$ 125,928	$ 51,605	$ 232,841	$ 101,765