Quarterly report pursuant to Section 13 or 15(d)

VARIABLE INTEREST ENTITIES Narrative (Details)

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VARIABLE INTEREST ENTITIES Narrative (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Dec. 31, 2015
Oct. 01, 2015
Dec. 31, 2011
Variable Interest Entity [Line Items]              
Operating revenues $ 63,351 $ 70,738 $ 125,933 $ 138,153      
Aeroleo              
Variable Interest Entity [Line Items]              
Economic interest percent             50.00%
Voting interest percent             20.00%
Aeroleo | Variable Interest Entity, Primary Beneficiary              
Variable Interest Entity [Line Items]              
Economic interest transferred, percent           50.00%  
Variable interest transferred, percent           80.00%  
Assets 15,900   15,900   $ 17,900    
Liabilities 9,300   9,300   $ 15,900    
Operating revenues 6,500   14,000        
Net gain (loss) from consolidation $ 1,400   $ 2,100        
Pro Forma              
Variable Interest Entity [Line Items]              
Operating revenues   82,004   160,744      
Pro Forma | Aeroleo | Variable Interest Entity, Primary Beneficiary              
Variable Interest Entity [Line Items]              
Operating revenues   $ 11,266   $ 22,591