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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019	Dec. 28, 2019
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 674,200	$ 692,139
Contract asset - costs and profits in excess of billings	144,777		$ 141,322
Contract liability - billings in excess of costs and earnings	151,034		$ 117,945
Revenue recognized from contract liability	18,240	1,030
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	445,135	467,361
Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	229,065	224,778
Utility Support Structures Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	222,948	243,258
Utility Support Structures Segment \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	8,924	30,292
Utility Support Structures Segment \| Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	214,024	212,966
Engineered Support Structures Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	227,366	227,969
Engineered Support Structures Segment \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	215,879	218,980
Engineered Support Structures Segment \| Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	11,487	8,989
Coatings Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	68,590	70,231
Coatings Segment \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	68,590	70,231
Coatings Segment \| Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Irrigation Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	155,296	150,681
Irrigation Segment \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	151,742	147,858
Irrigation Segment \| Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 3,554	$ 2,823