GOODWILL AND INTANGIBLE ASSETS - Carrying Amount of Goodwill by Segment (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Carrying amount of goodwill
Balance at the beginning of the period	$ 321,110
Foreign currency translation	12,317
Balance at the end of the period	336,754
Goodwill, Written off Related to Sale of Business Unit	(3,327)
Engineered Support Structures Segment
Carrying amount of goodwill
Balance at the beginning of the period	94,314
Foreign currency translation	4,568
Balance at the end of the period	102,209
Goodwill, Written off Related to Sale of Business Unit	(3,327)
Energy and Mining Segment
Carrying amount of goodwill
Balance at the beginning of the period	72,212
Foreign currency translation	6,704
Balance at the end of the period	78,916
Utility Support Structures Segment
Carrying amount of goodwill
Balance at the beginning of the period	75,404
Foreign currency translation	0
Balance at the end of the period	75,404
Goodwill, Written off Related to Sale of Business Unit	0
Coatings Segment
Carrying amount of goodwill
Balance at the beginning of the period	59,569
Foreign currency translation	951
Balance at the end of the period	60,520
Goodwill, Written off Related to Sale of Business Unit	0
Irrigation Segment
Carrying amount of goodwill
Balance at the beginning of the period	19,611
Foreign currency translation	94
Balance at the end of the period	19,705
Goodwill, Written off Related to Sale of Business Unit	$ 0