Quarterly report pursuant to Section 13 or 15(d)

INVESTMENT IN AL MASANE AL KOBRA MINING COMPANY ("AMAK") (Details)

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INVESTMENT IN AL MASANE AL KOBRA MINING COMPANY ("AMAK") (Details)
$ in Thousands
 3 Months Ended
Mar. 31, 2016
USD ($)
SAR / $
Mar. 31, 2015
USD ($)
Dec. 31, 2015
USD ($)
Schedule of Equity Method Investments [Line Items]      
Equity in income of AMAK $ 5,367 $ 59  
Results of Operations [Abstract]      
Loss from operations 6,145 9,733  
AMAK [Member]      
Investment in Al Masane Al Kobra Mining Company Amak [Line Items]      
Investment in AMAK $ 53,100   $ 47,700
AMAK [Member]      
Schedule of Equity Method Investments [Line Items]      
Percentage investment in AMAK 35.00%   35.00%
Exchange rate | SAR / $ 3.75    
Company's share of income (loss) reported by AMAK $ 5,030 (278)  
Amortization of difference between Company's investment in AMAK and Company's share of net assets of AMAK 337 337  
Equity in income of AMAK 5,367 59  
Results of Operations [Abstract]      
Sales 8,992 5,301  
Gross profit 191 1,712  
General, administrative and other 2,147 2,501  
Loss from operations (1,956) (789)  
Gain on settlement with former operator 16,225 0  
Net income (loss) 14,269 (789)  
Depreciation, depletion and amortization 2,700 5,000  
Net income before depreciation and amortization 16,978 $ 4,972  
Financial Position [Abstract]      
Current assets 22,459   $ 26,078
Noncurrent assets 257,049   259,527
Total assets 279,508   285,605
Current liabilities 2,467   22,740
Long term liabilities 89,271   89,364
Shareholders' equity 187,770   173,501
Total liabilities and Shareholders' equity $ 279,508   $ 285,605