RESTRUCTURING (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)
RESTRUCTURING
Restructuring Charges	$ 116	$ 231
CNG and Abilene Heavy Fabrications
RESTRUCTURING
Annual cost savings		575
Restructuring Charges	116	267
Remaining Costs	738	738
CNG and Abilene Heavy Fabrications | Cost of sales:
RESTRUCTURING
Restructuring Charges	116	231
Remaining Costs	702	702
CNG and Abilene Heavy Fabrications | Selling, general and administrative
RESTRUCTURING
Restructuring Charges		36
Remaining Costs	36	36
CNG and Abilene Heavy Fabrications | Facility costs | Cost of sales:
RESTRUCTURING
Restructuring Charges	64	146
Remaining Costs	270	270
CNG and Abilene Heavy Fabrications | Moving and remediation | Cost of sales:
RESTRUCTURING
Restructuring Charges	1	1
Remaining Costs	176	176
CNG and Abilene Heavy Fabrications | Salary and severance | Cost of sales:
RESTRUCTURING
Restructuring Charges		17
Remaining Costs	17	17
CNG and Abilene Heavy Fabrications | Salary and severance | Selling, general and administrative
RESTRUCTURING
Restructuring Charges		36
Remaining Costs	36	36
CNG and Abilene Heavy Fabrications | Depreciation | Cost of sales:
RESTRUCTURING
Restructuring Charges	51	67
Remaining Costs	$ 239	$ 239