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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenues (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017	Dec. 31, 2017	Dec. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 682,405,000	$ 712,737,000	$ 1,381,089,000	$ 1,350,210,000
Contract asset, current	92,585,000		92,585,000		$ 51,507,000
Contract with customer, liability, current	4,669		4,669			$ 7,368
Revenue recognized from contract liability			4,000
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	474,740,000		952,025,000
Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	207,665,000		429,064,000
Offshore and Other Complex Steel Structures
Disaggregation of Revenue [Line Items]
Contract asset, current						$ 16,165,000
Utility Support Structures Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	196,531,000	209,622,000	406,390,000	409,652,000
Utility Support Structures Segment \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0		0
Utility Support Structures Segment \| Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	196,531,000		406,390,000
Engineered Support Structures Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	246,041,000	231,278,000	461,957,000	424,354,000
Engineered Support Structures Segment \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	237,720,000		444,914,000
Engineered Support Structures Segment \| Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	8,321,000		17,043,000
Coatings Segment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	74,539,000	64,600,000	142,997,000	123,932,000
Coatings Segment \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	74,539,000		142,997,000
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	160,613,000	$ 186,165,000	346,665,000	$ 351,606,000
Irrigation Segment \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	157,800,000		341,034,000
Irrigation Segment \| Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2,813,000		5,631,000
Other Segments \| Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	4,681,000		23,080,000
Other Segments \| Transferred over Time
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 0		$ 0