Annual report pursuant to Section 13 and 15(d)

COMMITMENTS AND CONTINGENCIES (Details)

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COMMITMENTS AND CONTINGENCIES (Details)
ر.س in Millions
 12 Months Ended
Dec. 31, 2017
USD ($)
Railcar
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2017
SAR (ر.س)
Railcar
Dec. 31, 2016
SAR (ر.س)
Oct. 24, 2010
USD ($)
Oct. 24, 2010
SAR (ر.س)
Loss Contingencies [Line Items]              
Expenses for environmental monitoring, compliance, and improvements $ 593,000 $ 622,000 $ 604,000        
Operating Leases, Future Minimum Payments Receivable [Abstract]              
2018 3,393,000            
2019 3,341,000            
2020 3,250,000            
2021 3,120,000            
2022 1,498,000            
Thereafter 3,177,000            
Total 17,779,000            
Operating Leased Assets [Line Items]              
Operating lease, rental expense $ 4,400,000 4,200,000 $ 4,200,000        
Railcars [Member]              
Operating Leased Assets [Line Items]              
Number of railcars | Railcar 335     335      
Operating lease expiration date Dec. 31, 2026            
Total commitments under operating leases $ 17,800,000            
Operating lease period 9 years            
Office Space in Sugar Land, TX [Member]              
Operating Leased Assets [Line Items]              
Operating lease expiration date Dec. 31, 2018            
Total commitments under operating leases $ 10,000            
Other Equipment [Member]              
Operating Leased Assets [Line Items]              
Operating lease expiration date Dec. 31, 2020            
Total commitments under operating leases $ 50,000            
Pending Litigation [Member]              
Loss Contingencies [Line Items]              
Accrued recorded value 1,000,000            
Saudi Industrial Development Fund Limited Guarantee [Member]              
Guarantor Obligations [Line Items]              
Principal amount of loan guaranteed           $ 88,000,000 ر.س 330.0
Amount of maximum exposure $ 81,300,000 $ 82,700,000   ر.س 305.0 ر.س 310.0 $ 36,100,000 ر.س 135.3
Saudi Industrial Development Fund Limited Guarantee [Member] | Maximum [Member]              
Guarantor Obligations [Line Items]              
Loan guarantee           41.00% 41.00%