BUSINESS SEGMENTS (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 24, 2016 USD ($)	Jun. 25, 2016 USD ($)	Mar. 26, 2016 USD ($)	Dec. 26, 2015 USD ($)	Sep. 26, 2015 USD ($)	Jun. 27, 2015 USD ($)	Mar. 28, 2015 USD ($)	Dec. 31, 2016 USD ($) segment	Dec. 26, 2015 USD ($)	Dec. 27, 2014 USD ($)
Business Segments
Number of reportable segments | segment									5
Maximum percentage of sales of other businesses and activities to consolidated sales as basis for aggregation									10.00%
Net sales	$ 674,575,000	$ 610,247,000	$ 640,249,000	$ 596,605,000	$ 633,828,000	$ 632,575,000	$ 682,123,000	$ 670,398,000	$ 2,521,676,000	$ 2,618,924,000	$ 3,123,143,000
Operating Income									243,504,000	131,695,000	357,716,000
Interest expense, net									(41,304,000)	(41,325,000)	(30,744,000)
Costs associated with refinancing of debt									0	0	38,705,000
Other									18,254,000	2,637,000	(4,084,000)
Earnings before income taxes and equity in earnings of nonconsolidated subsidiaries									220,454,000	93,007,000	284,183,000
Total assets	2,391,731,000				2,392,382,000				2,391,731,000	2,392,382,000	2,721,955,000
Capital expenditures									57,920,000	45,468,000	73,023,000
Depreciation and amortization									82,417,000	91,144,000	89,328,000
Engineered Support Structures
Business Segments
Net sales									764,512,000	748,450,000	735,007,000
Operating Income									71,398,000	59,592,000	66,024,000
Total assets	610,366,000				611,201,000				610,366,000	611,201,000	640,132,000
Capital expenditures									16,045,000	11,445,000	11,849,000
Depreciation and amortization									21,048,000	22,810,000	22,363,000
Energy and Mining Segment
Business Segments
Net sales									314,532,000	333,207,000	443,688,000
Operating Income									11,851,000	(18,762,000)	41,342,000
Total assets	364,658,000				396,366,000				364,658,000	396,366,000	500,407,000
Capital expenditures									3,427,000	3,544,000	4,893,000
Depreciation and amortization									17,425,000	20,733,000	22,146,000
Utility Support Structures Segment
Business Segments
Net sales									630,782,000	673,338,000	822,565,000
Operating Income									69,077,000	37,847,000	95,118,000
Total assets	410,448,000				422,021,000				410,448,000	422,021,000	470,720,000
Capital expenditures									3,411,000	11,815,000	9,014,000
Depreciation and amortization									16,492,000	17,959,000	17,811,000
Coatings
Business Segments
Net sales									243,877,000	255,473,000	278,435,000
Operating Income									46,596,000	27,369,000	60,921,000
Total assets	274,666,000				270,793,000				274,666,000	270,793,000	301,707,000
Capital expenditures									24,873,000	6,836,000	14,029,000
Depreciation and amortization									12,883,000	12,962,000	14,615,000
Irrigation Segment
Business Segments
Net sales									567,973,000	605,771,000	839,717,000
Operating Income									87,835,000	84,537,000	151,508,000
Total assets	313,982,000				310,967,000				313,982,000	310,967,000	360,883,000
Capital expenditures									8,836,000	7,756,000	21,113,000
Depreciation and amortization									12,097,000	11,746,000	10,471,000
Other
Business Segments
Net sales									0	2,685,000	3,731,000
Operating Income									0	(9,802,000)	(1,535,000)
Total assets	0				2,267,000				0	2,267,000	4,930,000
Capital expenditures									0	1,396,000	1,181,000
Depreciation and amortization									0	570,000	123,000
Corporate
Business Segments
Operating Income									(43,253,000)	(49,086,000)	(55,662,000)
Total assets	417,611,000				378,767,000				417,611,000	378,767,000	443,176,000
Capital expenditures									1,328,000	2,676,000	10,944,000
Depreciation and amortization									2,472,000	4,364,000	1,799,000
Parent
Business Segments
Net sales									1,126,985,000	1,169,674,000	1,392,509,000
Operating Income									104,876,000	85,097,000	154,714,000
Other									1,480,000	(2,374,000)	2,021,000
Earnings before income taxes and equity in earnings of nonconsolidated subsidiaries									62,926,000	39,180,000	83,801,000
Total assets	$ 1,885,818,000				$ 1,866,376,000				1,885,818,000	1,866,376,000
Capital expenditures									9,031,000	14,362,000	41,260,000
Depreciation and amortization									27,096,000	29,433,000	24,509,000
Operating segment
Business Segments
Sales									2,619,398,000	2,705,722,000	3,269,256,000
Operating segment | Engineered Support Structures
Business Segments
Sales									800,525,000	771,453,000	809,970,000
Operating segment | Engineered Support Structures | Lighting, Traffic, and Roadway Products
Business Segments
Sales									632,455,000	600,280,000	648,352,000
Operating segment | Engineered Support Structures | Communication Products
Business Segments
Sales									168,070,000	171,173,000	161,618,000
Operating segment | Energy and Mining Segment
Business Segments
Sales									322,637,000	337,859,000	443,983,000
Operating segment | Energy and Mining Segment | Offshore and Other Complex Steel Structures
Business Segments
Sales									107,824,000	103,068,000	146,432,000
Operating segment | Energy and Mining Segment | Grinding Media
Business Segments
Sales									83,110,000	96,442,000	116,056,000
Operating segment | Energy and Mining Segment | Access Systems
Business Segments
Sales									131,703,000	138,349,000	181,495,000
Operating segment | Utility Support Structures Segment
Business Segments
Sales									631,551,000	674,577,000	825,016,000
Operating segment | Utility Support Structures Segment | Steel
Business Segments
Sales									541,295,000	578,996,000	714,427,000
Operating segment | Utility Support Structures Segment | Concrete
Business Segments
Sales									90,256,000	95,581,000	110,589,000
Operating segment | Coatings
Business Segments
Sales									289,481,000	302,385,000	333,853,000
Operating segment | Irrigation Segment
Business Segments
Sales									575,204,000	612,201,000	846,326,000
Operating segment | Other
Business Segments
Sales									0	7,247,000	10,108,000
Intersegment
Business Segments
Sales									97,722,000	86,798,000	146,113,000
Intersegment | Engineered Support Structures
Business Segments
Sales									36,013,000	23,003,000	74,963,000
Intersegment | Energy and Mining Segment
Business Segments
Sales									8,105,000	4,652,000	295,000
Intersegment | Utility Support Structures Segment
Business Segments
Sales									769,000	1,239,000	2,451,000
Intersegment | Coatings
Business Segments
Sales									45,604,000	46,912,000	55,418,000
Intersegment | Irrigation Segment
Business Segments
Sales									7,231,000	6,430,000	6,609,000
Intersegment | Other
Business Segments
Sales									$ 0	$ 4,562,000	$ 6,377,000