SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019	Dec. 28, 2019
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 733,970	$ 690,340	$ 2,096,978	$ 2,083,350
Contract assets	113,254		113,254		$ 141,322
Contract liabilties	153,619		153,619
Contract liabilities, current	116,470		116,470		$ 117,945
Revenue recognized from contract liability	16,333	314	55,610	2,242
Contract Liabilities
Disaggregation of Revenue [Line Items]
Contract liabilities, current	116,470		116,470
Other Noncurrent Liabilities
Disaggregation of Revenue [Line Items]
Contract liabilities, noncurrent	37,149		37,149
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	490,769	471,934	1,385,005	1,422,365
Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	243,201	218,406	711,973	660,985
Utility Support Structures Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	272,479	204,196	723,900	656,463
Utility Support Structures Segment | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	43,287	3,418	56,830	43,642
Utility Support Structures Segment | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	229,192	200,778	667,070	612,821
Engineered Support Structures Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	254,945	266,494	731,184	752,028
Engineered Support Structures Segment | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	244,785	252,501	697,491	713,574
Engineered Support Structures Segment | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	10,160	13,993	33,693	38,454
Coatings Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	68,698	76,922	199,955	228,242
Coatings Segment | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	68,698	76,922	199,955	228,242
Coatings Segment | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Irrigation Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	137,848	142,728	441,939	446,617
Irrigation Segment | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	133,999	139,093	430,729	436,907
Irrigation Segment | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 3,849	$ 3,635	$ 11,210	$ 9,710